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‎README.md

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@@ -356,6 +356,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
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|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
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|-|-|-|-|-|-
359+
| 0121 |[Best Time to Buy and Sell Stock](src/main/ruby/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1) | 147 | 80.21
359360

360361
####Day 8
361362

@@ -484,6 +485,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
484485

485486
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
486487
|-|-|-|-|-|-
488+
| 0104 |[Maximum Depth of Binary Tree](src/main/ruby/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H) | 55 | 96.72
487489

488490
####Day 11 Containers and Libraries
489491

@@ -751,11 +753,13 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
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752754
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
753755
|-|-|-|-|-|-
756+
| 0121 |[Best Time to Buy and Sell Stock](src/main/ruby/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1) | 147 | 80.21
754757

755758
####Day 6 Tree
756759

757760
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
758761
|-|-|-|-|-|-
762+
| 0102 |[Binary Tree Level Order Traversal](src/main/ruby/g0101_0200/s0102_binary_tree_level_order_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 66 | 76.43
759763

760764
####Day 7 Binary Search
761765

@@ -887,6 +891,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
887891

888892
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
889893
|-|-|-|-|-|-
894+
| 0101 |[Symmetric Tree](src/main/ruby/g0101_0200/s0101_symmetric_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 58 | 91.34
890895

891896
####Day 16 Design
892897

@@ -922,6 +927,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
922927

923928
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
924929
|-|-|-|-|-|-
930+
| 0136 |[Single Number](src/main/ruby/g0101_0200/s0136_single_number/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1) | 68 | 78.44
925931
| 0007 |[Reverse Integer](src/main/ruby/g0001_0100/s0007_reverse_integer/solution.rb)| Medium | Top_Interview_Questions, Math | 58 | 75.27
926932
| 0009 |[Palindrome Number](src/main/ruby/g0001_0100/s0009_palindrome_number/solution.rb)| Easy | Math | 83 | 74.19
927933

@@ -944,6 +950,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
944950

945951
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
946952
|-|-|-|-|-|-
953+
| 0121 |[Best Time to Buy and Sell Stock](src/main/ruby/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1) | 147 | 80.21
947954
| 0001 |[Two Sum](src/main/ruby/g0001_0100/s0001_two_sum/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n) | 57 | 89.38
948955
| 0055 |[Jump Game](src/main/ruby/g0001_0100/s0055_jump_game/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 88 | 95.88
949956
| 0075 |[Sort Colors](src/main/ruby/g0001_0100/s0075_sort_colors/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n)_Space_O(1) | 54 | 88.46
@@ -980,6 +987,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
980987

981988
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
982989
|-|-|-|-|-|-
990+
| 0114 |[Flatten Binary Tree to Linked List](src/main/ruby/g0101_0200/s0114_flatten_binary_tree_to_linked_list/solution.rb)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Big_O_Time_O(N)_Space_O(N) | 47 | 100.00
983991
| 0024 |[Swap Nodes in Pairs](src/main/ruby/g0001_0100/s0024_swap_nodes_in_pairs/solution.rb)| Medium | Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(1) | 59 | 76.00
984992
| 0021 |[Merge Two Sorted Lists](src/main/ruby/g0001_0100/s0021_merge_two_sorted_lists/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(m+n)_Space_O(m+n) | 66 | 59.01
985993
| 0025 |[Reverse Nodes in k-Group](src/main/ruby/g0001_0100/s0025_reverse_nodes_in_k_group/solution.rb)| Hard | Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(k) | 62 | 91.67
@@ -989,6 +997,9 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
989997
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
990998
|-|-|-|-|-|-
991999
| 0094 |[Binary Tree Inorder Traversal](src/main/ruby/g0001_0100/s0094_binary_tree_inorder_traversal/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Big_O_Time_O(n)_Space_O(n) | 56 | 84.00
1000+
| 0102 |[Binary Tree Level Order Traversal](src/main/ruby/g0101_0200/s0102_binary_tree_level_order_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 66 | 76.43
1001+
| 0104 |[Maximum Depth of Binary Tree](src/main/ruby/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H) | 55 | 96.72
1002+
| 0124 |[Binary Tree Maximum Path Sum](src/main/ruby/g0101_0200/s0124_binary_tree_maximum_path_sum/solution.rb)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 71 | 98.00
9921003
| 0098 |[Validate Binary Search Tree](src/main/ruby/g0001_0100/s0098_validate_binary_search_tree/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 68 | 70.23
9931004

9941005
####Udemy Trie and Heap
@@ -1048,6 +1059,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
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10491060
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
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|-|-|-|-|-|-
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| 0121 |[Best Time to Buy and Sell Stock](src/main/ruby/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1) | 147 | 80.21
10511063

10521064
####Day 4 Array
10531065

@@ -1092,6 +1104,9 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
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10931105
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
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|-|-|-|-|-|-
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| 0102 |[Binary Tree Level Order Traversal](src/main/ruby/g0101_0200/s0102_binary_tree_level_order_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 66 | 76.43
1108+
| 0104 |[Maximum Depth of Binary Tree](src/main/ruby/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H) | 55 | 96.72
1109+
| 0101 |[Symmetric Tree](src/main/ruby/g0101_0200/s0101_symmetric_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 58 | 91.34
10951110

10961111
####Day 12 Tree
10971112

@@ -1115,6 +1130,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
11151130

11161131
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
11171132
|-|-|-|-|-|-
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| 0136 |[Single Number](src/main/ruby/g0101_0200/s0136_single_number/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1) | 68 | 78.44
11181134
| 0015 |[3Sum](src/main/ruby/g0001_0100/s0015_3sum/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n\*log(n))_Space_O(n^2) | 659 | 83.74
11191135

11201136
####Day 2 Array
@@ -1194,6 +1210,7 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
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11951211
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
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|-|-|-|-|-|-
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| 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/ruby/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Big_O_Time_O(N)_Space_O(N) | 71 | 91.78
11971214

11981215
####Day 16 Tree
11991216

@@ -1302,11 +1319,22 @@ Ruby-based LeetCode algorithm problem solutions, regularly updated.
13021319

13031320
|<!----> |<!----> |<!----> |<!----> |<!----> |<!---->
13041321
|-|-|-|-|-|-
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| 0136 |[Single Number](src/main/ruby/g0101_0200/s0136_single_number/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1) | 68 | 78.44
13051323

13061324
##Algorithms
13071325

13081326
| # | Title | Difficulty | Tag | Time, ms | Time, %
13091327
|------|----------------|-------------|-------------|----------|---------
1328+
| 0136 |[Single Number](src/main/ruby/g0101_0200/s0136_single_number/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Data_Structure_II_Day_1_Array, Algorithm_I_Day_14_Bit_Manipulation, Udemy_Integers, Big_O_Time_O(N)_Space_O(1) | 68 | 78.44
1329+
| 0131 |[Palindrome Partitioning](src/main/ruby/g0101_0200/s0131_palindrome_partitioning/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Big_O_Time_O(N\*2^N)_Space_O(2^N\*N) | 1192 | 63.64
1330+
| 0128 |[Longest Consecutive Sequence](src/main/ruby/g0101_0200/s0128_longest_consecutive_sequence/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Union_Find, Big_O_Time_O(N_log_N)_Space_O(1) | 135 | 91.36
1331+
| 0124 |[Binary Tree Maximum Path Sum](src/main/ruby/g0101_0200/s0124_binary_tree_maximum_path_sum/solution.rb)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(N)_Space_O(N) | 71 | 98.00
1332+
| 0121 |[Best Time to Buy and Sell Stock](src/main/ruby/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Data_Structure_I_Day_3_Array, Dynamic_Programming_I_Day_7, Level_1_Day_5_Greedy, Udemy_Arrays, Big_O_Time_O(N)_Space_O(1) | 147 | 80.21
1333+
| 0114 |[Flatten Binary Tree to Linked List](src/main/ruby/g0101_0200/s0114_flatten_binary_tree_to_linked_list/solution.rb)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Udemy_Linked_List, Big_O_Time_O(N)_Space_O(N) | 47 | 100.00
1334+
| 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/ruby/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Data_Structure_II_Day_15_Tree, Big_O_Time_O(N)_Space_O(N) | 71 | 91.78
1335+
| 0104 |[Maximum Depth of Binary Tree](src/main/ruby/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Programming_Skills_I_Day_10_Linked_List_and_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(N)_Space_O(H) | 55 | 96.72
1336+
| 0102 |[Binary Tree Level Order Traversal](src/main/ruby/g0101_0200/s0102_binary_tree_level_order_traversal/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_1_Day_6_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(N)_Space_O(N) | 66 | 76.43
1337+
| 0101 |[Symmetric Tree](src/main/ruby/g0101_0200/s0101_symmetric_tree/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_2_Day_15_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 58 | 91.34
13101338
| 0098 |[Validate Binary Search Tree](src/main/ruby/g0001_0100/s0098_validate_binary_search_tree/solution.rb)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Data_Structure_I_Day_14_Tree, Level_1_Day_8_Binary_Search_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(N)_Space_O(log(N)) | 68 | 70.23
13111339
| 0096 |[Unique Binary Search Trees](src/main/ruby/g0001_0100/s0096_unique_binary_search_trees/solution.rb)| Medium | Top_100_Liked_Questions, Dynamic_Programming, Math, Tree, Binary_Tree, Binary_Search_Tree, Dynamic_Programming_I_Day_11, Big_O_Time_O(n)_Space_O(1) | 57 | 61.54
13121340
| 0094 |[Binary Tree Inorder Traversal](src/main/ruby/g0001_0100/s0094_binary_tree_inorder_traversal/solution.rb)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Data_Structure_I_Day_10_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(n)_Space_O(n) | 56 | 84.00

‎src/main/ruby/com_github_leetcode/tree_node.rb

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@@ -2,9 +2,50 @@
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classTreeNode
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attr_accessor:val,:left,:right
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5-
definitialize(val=0,left=nil,right=nil)
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definitialize(val,left=nil,right=nil)
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@val=val
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@left=left
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@right=right
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end
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defself.create(tree_values)
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returnniliftree_values.empty?
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root=TreeNode.new(tree_values[0])
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queue=[root]
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i=1
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whilei <tree_values.length
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curr=queue.shift
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iftree_values[i]
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curr.left=TreeNode.new(tree_values[i])
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queue.push(curr.left)
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end
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i +=1
27+
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ifi <tree_values.length &&tree_values[i]
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curr.right=TreeNode.new(tree_values[i])
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queue.push(curr.right)
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end
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i +=1
34+
end
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root
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end
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defto_s
40+
returnval.to_sifleft.nil? &&right.nil?
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root=val.to_s
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left_value='null'
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right_value='null'
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left_value=left.to_sifleft
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right_value=right.to_sifright
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"#{root},#{left_value},#{right_value}"
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end
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end
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101\. Symmetric Tree
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Easy
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Given the`root` of a binary tree,_check whether it is a mirror of itself_ (i.e., symmetric around its center).
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2021/02/19/symtree1.jpg)
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**Input:** root =[1,2,2,3,4,4,3]
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**Output:** true
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**Example 2:**
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![](https://assets.leetcode.com/uploads/2021/02/19/symtree2.jpg)
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**Input:** root =[1,2,2,null,3,null,3]
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**Output:** false
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**Constraints:**
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* The number of nodes in the tree is in the range`[1, 1000]`.
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*`-100 <= Node.val <= 100`
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**Follow up:** Could you solve it both recursively and iteratively?
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# #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Depth_First_Search #Breadth_First_Search
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# #Tree #Binary_Tree #Data_Structure_I_Day_11_Tree #Level_2_Day_15_Tree
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# #Big_O_Time_O(N)_Space_O(log(N)) #2023_11_23_Time_58_ms_(91.34%)_Space_211.1_MB_(48.82%)
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# Definition for a binary tree node.
6+
# class TreeNode
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# attr_accessor :val, :left, :right
8+
# def initialize(val = 0, left = nil, right = nil)
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# @val = val
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# @left = left
11+
# @right = right
12+
# end
13+
# end
14+
# @param {TreeNode} root
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# @return {Boolean}
16+
defis_symmetric(root)
17+
returntrueifroot.nil?
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helper_symmetric(root.left,root.right)
20+
end
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private
23+
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defhelper_symmetric(left_node,right_node)
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returnleft_node.nil? &&right_node.nil?ifleft_node.nil? ||right_node.nil?
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returnfalseifleft_node.val !=right_node.val
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helper_symmetric(left_node.left,right_node.right) &&helper_symmetric(left_node.right,right_node.left)
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end
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102\. Binary Tree Level Order Traversal
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Medium
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Given the`root` of a binary tree, return_the level order traversal of its nodes' values_. (i.e., from left to right, level by level).
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg)
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**Input:** root =[3,9,20,null,null,15,7]
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**Output:**[[3],[9,20],[15,7]]
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**Example 2:**
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**Input:** root =[1]
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**Output:**[[1]]
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**Example 3:**
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**Input:** root =[]
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**Output:**[]
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**Constraints:**
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* The number of nodes in the tree is in the range`[0, 2000]`.
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*`-1000 <= Node.val <= 1000`
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# #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Breadth_First_Search #Tree
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# #Binary_Tree #Data_Structure_I_Day_11_Tree #Level_1_Day_6_Tree #Udemy_Tree_Stack_Queue
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# #Big_O_Time_O(N)_Space_O(N) #2023_11_23_Time_66_ms_(76.43%)_Space_211.3_MB_(57.86%)
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# Definition for a binary tree node.
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# class TreeNode
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# attr_accessor :val, :left, :right
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# def initialize(val = 0, left = nil, right = nil)
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# @val = val
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# @left = left
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# @right = right
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# end
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# end
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# @param {TreeNode} root
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# @return {Integer[][]}
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deflevel_order(root)
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result=[]
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returnresultifroot.nil?
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queue=[root,nil]
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level=[]
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untilqueue.empty?
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current=queue.shift
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ifcurrent.nil?
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result <<level.dup
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level.clear
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queue.push(nil)unlessqueue.empty?
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else
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level <<current.val
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queue.push(current.left)ifcurrent.left
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queue.push(current.right)ifcurrent.right
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end
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end
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result
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end
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104\. Maximum Depth of Binary Tree
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Easy
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Given the`root` of a binary tree, return_its maximum depth_.
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A binary tree's**maximum depth** is the number of nodes along the longest path from the root node down to the farthest leaf node.
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2020/11/26/tmp-tree.jpg)
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**Input:** root =[3,9,20,null,null,15,7]
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**Output:** 3
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**Example 2:**
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**Input:** root =[1,null,2]
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**Output:** 2
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**Example 3:**
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**Input:** root =[]
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**Output:** 0
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**Example 4:**
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**Input:** root =[0]
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**Output:** 1
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**Constraints:**
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* The number of nodes in the tree is in the range <code>[0, 10<sup>4</sup>]</code>.
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*`-100 <= Node.val <= 100`
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# #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Depth_First_Search #Breadth_First_Search
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# #Tree #Binary_Tree #Data_Structure_I_Day_11_Tree
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# #Programming_Skills_I_Day_10_Linked_List_and_Tree #Udemy_Tree_Stack_Queue
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# #Big_O_Time_O(N)_Space_O(H) #2023_11_23_Time_55_ms_(96.72%)_Space_211.3_MB_(37.23%)
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# Definition for a binary tree node.
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# class TreeNode
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# attr_accessor :val, :left, :right
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# def initialize(val = 0, left = nil, right = nil)
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# @val = val
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# @left = left
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# @right = right
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# end
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# end
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# @param {TreeNode} root
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# @return {Integer}
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defmax_depth(root)
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find_depth(root,0)
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end
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private
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deffind_depth(node,current_depth)
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return0ifnode.nil?
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current_depth +=1
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1 +[find_depth(node.left,current_depth),find_depth(node.right,current_depth)].max
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end

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