1、两数之和

  1. var twoSum = function(nums, target) {
  2.   const map = new Map();
  3.   for(let i=0;i<nums.length;i++){
  4.     const complement = target - nums[i];
  5.     if(map.has(complement)){
  6.       return [map.get(complement),i]
  7.     }else{
  8.       map.set(nums[i],i)
  9.     }
  10.   }
  11.   return []
  12. };

2、两数相加

  1. var addTwoNumbers = function(l1, l2) {
  2.   let dummy = new ListNode();
  3.   let curr = dummy;
  4.   let carry = 0;
  5.   while(l1 !== null || l2 !== null){
  6.     let sum = 0;
  7.     if(l1 !== null){
  8.       sum+=l1.val
  9.       l1 = l1.next
  10.     }
  11.     if(l2 !== null){
  12.       sum+=l2.val
  13.       l2 = l2.next
  14.     }
  15.     sum+=carry;
  16.     curr.next = new ListNode(sum % 10);
  17.     carry = Math.floor(sum/10);
  18.     curr = curr.next;
  19.   }
  20.   if(carry > 0){
  21.     curr.next = new ListNode(carry);
  22.   }
  23.   return dummy.next;
  24. };

3、无重复字符串的最长字符串

  1. var lengthOfLongestSubstring = function(s) {
  2.     const set = new Set();
  3.     let i=0,j=0,maxLength=0;
  4.     if(s.length === 0){
  5.         return 0;
  6.     }
  7.     for(i;i<s.length;i++){
  8.         if(!set.has(s[i])){
  9.             set.add(s[i]);
  10.             maxLength = Math.max(maxLength,set.size);
  11.         }else{
  12.             while(set.has(s[i])){
  13.                 set.delete(s[j]);
  14.                 j++;
  15.             }
  16.             set.add(s[i]);
  17.         }
  18.     }
  19.     return maxLength;
  20. };

4、最长回文字符串

  1. var longestPalindrome = function(s) {
  2.   if(s.length<2){
  3.       return s;
  4.   }
  6.   let maxLength = 1;
  7.   let start = 0;
  9.   expandAroundCenter = function(left,right){
  10.       while(left>=0 && right<s.length && s[left]===s[right]){
  11.           if(right-left+1>maxLength){
  12.               maxLength = right-left+1;
  13.               start = left;
  14.           }
  15.           left--;
  16.           right++;
  17.       }
  18.   }
  20.   for(let i=0;i<s.length;i++){
  21.     expandAroundCenter(i-1,i+1);
  22.     expandAroundCenter(i,i+1);
  23.   }
  25.   return s.substring(start,start + maxLength);
  26. };