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Added Java 617,7,146#267

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Merged
neetcode-gh merged 7 commits intoneetcode-gh:mainfrommiladra:main
Jul 2, 2022
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25 changes: 25 additions & 0 deletionsjava/139-Word- Break.java
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class Solution {
public boolean wordBreak(String s, List<String> wordDict) {
boolean[] dp = new boolean[s.length() + 1];
Set<String> workDictSet = new HashSet<>(wordDict);

for(int i=0; i<dp.length ; i++){
dp[i] = false;
}

dp[s.length()] = true;

for(int i= s.length() -1 ; i>=0; i--){
for(String word : wordDict){
if( ((i + word.length()) <= s.length())
&& (s.substring(i , i + word.length()).startsWith(word))){
dp[i] = dp[i + word.length()];
}
if(dp[i]){
break;
}
}
}
return dp[0];
}
}
91 changes: 91 additions & 0 deletionsjava/146-LRU-Cache.java
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class LRUCache {

private Map<Integer,Node> cache;
private int capacity;

private Node left;
private Node right;

public LRUCache(int capacity) {
this.capacity = capacity;
cache = new HashMap<>();

//left = LRU , right = most recent
this.left = new Node(0,0);
this.right = new Node(0,0);
this.left.next = this.right;
this.right.prev = this.left;

}

public int get(int key) {

if(cache.containsKey(key)){
remove(cache.get(key));
insert(cache.get(key));
return cache.get(key).val;

} else{
return -1;
}

}

public void put(int key, int value) {

if(cache.containsKey(key)){
remove(cache.get(key));
}
cache.put(key , new Node(key , value));
insert(cache.get(key));

if(cache.size() > capacity){
// remove from the list and delte the LRU from the hashmap
Node lru = this.left.next;
remove(lru);
cache.remove(lru.key);

}


}

// remove node from list
public void remove(Node node) {

Node prev = node.prev;
Node next = node.next;

prev.next = next;
next.prev = prev;
}

// insert node at right
public void insert(Node node) {

Node prev = this.right.prev;
Node next = this.right;


prev.next = node;
next.prev = node;

node.next =next;
node.prev =prev;



}
private class Node{
private int key;
private int val;

Node next;
Node prev;

public Node(int key , int val){
this.key = key;
this.val = val;
}
}
}
44 changes: 44 additions & 0 deletionsjava/155-Min-Stack.java
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class MinStack {

private Stack<Integer> stack;
private Stack<Integer> minStack;

public MinStack() {
stack = new Stack<>();
minStack = new Stack<>();

}

public void push(int val) {
stack.push(val);

// The min stack may be empty, so we need to check it
val = Math.min(val, minStack.isEmpty() ? val : minStack.peek());
minStack.push(val);

}

public void pop() {
stack.pop();
minStack.pop();

}

public int top() {
return stack.peek();
}

public int getMin() {
return minStack.peek();

}
}

/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.push(val);
* obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.getMin();
*/
41 changes: 41 additions & 0 deletionsjava/202-Happy-Number.java
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class Solution {
public boolean isHappy(int n) {

if (n == 1 || n == -1) {
return true;
}

Set<Integer> visit = new HashSet<Integer>();

// compute square until getting duplicate value
while (!visit.contains(n)) {
visit.add(n);
// using helper function to compute the sum of squares
n = sumOfSquare(n);

if (n == 1)
return true;

}

return false;

}

public int sumOfSquare(int n) {

int output = 0;

while (n != 0) {
int digit = n % 10;
digit = digit * digit;
output += digit;
n = n / 10;

}

return output;

}

}
43 changes: 43 additions & 0 deletionsjava/234-Palindrome-Linked-List.java
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class Solution {
public boolean isPalindrome(ListNode head) {

ListNode fast = head;
ListNode slow = head;

while (fast != null && fast.next != null) {

// fast pointer shifted twice
fast = fast.next;
fast = fast.next;

// slow pointer shifted only once
slow = slow.next;

}

// reverse second half
ListNode prev = null;
while (slow != null) {
ListNode tmp = slow.next;
slow.next = prev;
prev = slow;
slow = tmp;
}

ListNode left = head;
ListNode right = prev;

while (right != null) {
if (left.val != right.val) {
return false;
}

left = left.next;
right = right.next;

}

return true;

}
}
21 changes: 21 additions & 0 deletionsjava/617-Merge-Two-Binary-Trees.java
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class Solution {
public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {

if(root1 == null && root2 == null) return null;

int val1 = root1 != null ? root1.val : 0;
int val2 = root2 != null ? root2.val : 0;

TreeNode root = new TreeNode(val1+val2);

// merge left side of trees if they are not null
root.left = mergeTrees((root1 != null && root1.left != null) ? root1.left : null , (root2 != null && root2.left != null) ? root2.left : null);

// merge righ side of trees if they are not null
root.right = mergeTrees((root1 != null && root1.right != null) ? root1.right : null , (root2 !=null && root2.right != null) ? root2.right: null );

return root;
}
}


26 changes: 26 additions & 0 deletionsjava/7-Reverse-Integer.java
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class Solution {
public int reverse(int x) {

int min = Integer.MIN_VALUE;
int max = Integer.MAX_VALUE;


int res = 0;
while(x!=0){
int digit = x % 10;
x = x / 10;

if((res> max / 10) || (res == max / 10 && digit >= max % 10))
return 0;

if((res < min / 10) || (res== min / 10 && digit <= min % 10))
return 0;


res = (res * 10) + digit;
}

return res;

}
}
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