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Commit403abae

Browse files
committed
add 23, 25, 32 modified 21, 24
1 parent8b8f1d9 commit403abae

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6 files changed

+124
-46
lines changed

6 files changed

+124
-46
lines changed

‎Easy/21-mergeSortedLists.js‎

Lines changed: 3 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -13,50 +13,7 @@
1313
varmergeTwoLists=function(l1,l2){
1414
varl3=newListNode();
1515
varl3Head=l3;
16-
if(l1===null&&l2===null){
17-
returnnull;
18-
}
19-
while(true){
20-
if(l1===null&&l2!==null){
21-
l3.val=l2.val;
22-
l2=l2.next;
23-
}elseif(l2===null&&l1!==null){
24-
l3.val=l1.val;
25-
l1=l1.next;
26-
}elseif(l1.val<=l2.val){
27-
l3.val=l1.val;
28-
l1=l1.next;
29-
}else{
30-
l3.val=l2.val;
31-
l2=l2.next;
32-
}
33-
if(l1===null&&l2===null){
34-
break;
35-
}
36-
l3.next=newListNode();
37-
l3=l3.next;
38-
}
39-
40-
returnl3Head;
41-
};
42-
43-
// discard first dummy node in the new list which contains the merged result.
44-
// this is good and straightforward
45-
varmergeTwoLists=function(l1,l2){
46-
varl3=newListNode();
47-
varl3Head=l3;
48-
while(true){
49-
if(l1===null&&l2===null){
50-
break;
51-
}
52-
if(l1===null&&l2!==null){
53-
l3.next=l2;
54-
break;
55-
}
56-
if(l2===null&&l1!==null){
57-
l3.next=l1;
58-
break;
59-
}
16+
while(l1&&l2){
6017
if(l1.val<=l2.val){
6118
l3.next=l1;
6219
l1=l1.next;
@@ -66,6 +23,8 @@ var mergeTwoLists = function(l1, l2) {
6623
}
6724
l3=l3.next;
6825
}
26+
if(!l1)l3.next=l2;
27+
if(!l2)l3.next=l1
6928

7029
returnl3Head.next;
7130
};

‎Medium/24-swapNodesPairs.js‎renamed to ‎Easy/24-swapNodesPairs.js‎

Lines changed: 32 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -30,3 +30,35 @@ var swapPairs = function(head) {
3030

3131
returnnewHead;
3232
};
33+
34+
// re write
35+
varswapPairs=function(head){
36+
if(!head||!head.next)returnhead;
37+
varp=head;
38+
varpPrev=head;
39+
varnewHead=head.next;
40+
while(p){
41+
varpNext=p.next;
42+
if(pNext){
43+
pPrev.next=pNext;
44+
p.next=pNext.next;
45+
pNext.next=p;
46+
pPrev=p;
47+
p=p.next;
48+
}else{
49+
break;
50+
}
51+
}
52+
53+
returnnewHead;
54+
};
55+
56+
// recursion version, clean Code
57+
varswapPairs=function(head){
58+
if(!head||!head.next)returnhead;
59+
varp=head;
60+
varpNext=p.next;
61+
p.next=swapPairs(pNext.next);
62+
pNext.next=p;
63+
returnpNext;
64+
};

‎Hard/23-MergeKSortedLists.js‎

Lines changed: 44 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,44 @@
1+
/*
2+
* Key: using priority queue is a commonly used solution and it has N*O(logK)
3+
* However, in JavaScript, there is no existing priority queue implementation,
4+
* so the new idea is to merge two sorted list every time. divide the lists into two
5+
* halves (divide-and-conque), and merge the two halves. Recursively merge.
6+
*
7+
* Definition for singly-linked list.
8+
* function ListNode(val) {
9+
* this.val = val;
10+
* this.next = null;
11+
* }
12+
*/
13+
/**
14+
*@param {ListNode[]} lists
15+
*@return {ListNode}
16+
*/
17+
varmergeKLists=function(lists){
18+
if(lists.length===0)returnlists;
19+
if(lists.length===1)returnlists[0];
20+
if(lists.length===2)returnmergeTwoLists(lists[0],lists[1]);
21+
varlistNums=lists.length;
22+
varfirstHalf=lists.slice(0,Math.floor(listNums/2));
23+
varsecondHalf=lists.slice(Math.floor(listNums/2),listNums);
24+
returnmergeTwoLists(mergeKLists(firstHalf),mergeKLists(secondHalf));
25+
};
26+
27+
varmergeTwoLists=function(l1,l2){
28+
varl3=newListNode();
29+
varl3Head=l3;
30+
while(l1&&l2){
31+
if(l1.val<=l2.val){
32+
l3.next=l1;
33+
l1=l1.next;
34+
}else{
35+
l3.next=l2;
36+
l2=l2.next;
37+
}
38+
l3=l3.next;
39+
}
40+
if(!l1)l3.next=l2;
41+
if(!l2)l3.next=l1
42+
43+
returnl3Head.next;
44+
};

‎Hard/25-reverseNodesInKGroup.js‎

Whitespace-only changes.

‎Hard/32-longestValidParentheses.js‎

Lines changed: 41 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,41 @@
1+
/**
2+
*@param {string} s
3+
*@return {number}
4+
*/
5+
varlongestValidParentheses=function(s){
6+
varstack=[];
7+
varresult=0;
8+
varmaxLength=0;
9+
10+
for(vari=0;i<s.length;i++){
11+
if(s[i]==='('){
12+
stack.push(i);
13+
}
14+
if(s[i]===')'){
15+
if(stack.length>0){
16+
if(s[stack[stack.length-1]]==='('){
17+
stack.pop();
18+
}else{
19+
stack.push(i);
20+
}
21+
}elseif(stack.length===0){
22+
stack.push(i);
23+
}
24+
}
25+
}
26+
27+
if(stack.length===0)returns.length;
28+
29+
varright=s.length;
30+
while(stack.length>0){
31+
varleft=stack[stack.length-1];
32+
maxLength=right-left-1;
33+
result=Math.max(maxLength,result);
34+
right=stack.pop();
35+
}
36+
if(stack.length===0){
37+
result=Math.max(result,right);
38+
}
39+
40+
returnresult;
41+
};

‎README.md‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -75,7 +75,6 @@
7575
*[16. 3Sum Closest](https://leetcode.com/problems/3sum-closest/) -[Solution](./Medium/16-3sumClosest.js)
7676
*[17. Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) -[Solution](./Medium/17-LetterCombinationsPhoneNumber.js)
7777
*[22. Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) -[Solution](./Medium/22-generateParentheses.js)
78-
*[24. Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/) -[Solution](./Medium/24-swapNodesPairs.js)
7978
*[29. Divide Two Integers](https://leetcode.com/problems/divide-two-integers/) -[Solution](./Medium/29-DivideTwoIntegers.js)
8079
*[31. Next Permutation](https://leetcode.com/problems/next-permutation/) -[Solution](./Medium/31-nextPermutation.js)
8180
*[31. Next Permutation](https://leetcode.com/problems/next-permutation/) -[Solution](./Medium/31-nextPermutation.js)
@@ -122,4 +121,7 @@
122121
*[337. House Robber III](https://leetcode.com/problems/house-robber-iii/) -[Solution](./Medium/337-houseRobberIII.js)
123122

124123
#####Hard
125-
*[33. Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/) -[Solution](./Medium/33-searchRotatedSortedArray.js)
124+
*[23. Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/) -[Solution](./Hard/23-MergeKSortedLists.js)
125+
*[25. Reverse Nodes in k-Group](https://leetcode.com/problems/reverse-nodes-in-k-group/) -[Solution](./Hard/25-reverseNodesInKGroup.js)
126+
*[32. Longest Valid Parentheses](https://leetcode.com/problems/longest-valid-parentheses/) -[Solution](./Hard/32-longestValidParentheses.js)
127+
*[33. Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/) -[Solution](./Hard/33-searchRotatedSortedArray.js)

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