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).

 

 

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与3Sum相同的思路

每一轮先固定一个数，用双指针指向数组的头和尾。

如果目前三个数的和小于target，头指针++，否则尾指针--，直到指针碰到为止，记录最接近的结果。

1 /** 2  * @param {number[]} nums 3  * @param {number} target 4  * @return {number} 5  */ 6 var threeSumClosest = function(nums, target) { 7     var min = Infinity; 8     var res = 0; 9     nums = nums.sort(sorting);10 11     for(var i = 0; i < nums.length - 2; i++){12         if(nums[i - 1] !== undefined && nums[i - 1] === nums[i]){13             continue;14         }15         var curr = nums[i];16         var m = i + 1;17         var n = nums.length - 1;18         while(m < n){19             var tmp = Math.abs(nums[m] + nums[n] + curr - target);20             if(tmp < min){21                 min = tmp;22                 res = nums[m] + nums[n] + curr;23             }24 25             if(nums[m] + nums[n] + curr < target){26                 m++;27             } else {28                 n--;29             }30         }31     }32     return res;33 34     function sorting(a, b){35         if(a > b){36             return 1;37         }else if(a < b){38             return -1;39         }else{40             return 0;41         }42     }43 };