16. 3Sum Closest

Posted 2020-10-10 暗影侠客

16. 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

 1 /**
 2  * @param {number[]} nums
 3  * @param {number} target
 4  * @return {number}
 5  */
 6 var threeSumClosest = function(nums, target) {
 7     
 8     //几乎和threeSum问题一样，但是这个问题有个好处就是只有唯一解
 9     var len = nums.length;
10     var res = Number.MAX_VALUE;
11     var local = Number.MAX_VALUE;
12     nums.sort(function(a,b){ return a-b;});
13     
14     for(var i = 0;i < len;i++){
15         
16           //转成twoSum 问题
17           var temp = target - nums[i];
18         
19           var left = i + 1; var right = len - 1;
20         
21          //双指针解法
22          while(left < right){
23              
24               var l = nums[left];
25               var r = nums[right];
26               var tempsum = l + r;
27              
28               if(tempsum == temp){                  
29                   return target;
30               }else if(tempsum < temp){                  
31                   left++;      
32               }else{
33                   right--;
34               }
35              
36              
37              if(Math.abs(tempsum+nums[i] - target) < local){
38                  
39                  local = Math.abs(tempsum+nums[i] - target);
40                  res = tempsum+nums[i];
41              }
42                  
43                
44            
45          }     
46         
47     }
48                  
49         return res;
50     
51 };