[LeetCode][JavaScript]3Sum Closest

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).

https://leetcode.com/problems/3sum-closest/

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与3Sum相同的思路http://www.cnblogs.com/Liok3187/p/4540921.html

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。

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function(nums, target) {
    var min = Infinity;
    var res = 0;
    nums = nums.sort(sorting);

    for(var i = 0; i < nums.length - 2; i++){
        if(nums[i - 1] !== undefined && nums[i - 1] === nums[i]){
            continue;
        }
        var curr = nums[i];
        var m = i + 1;
        var n = nums.length - 1;
        while(m < n){
            var tmp = Math.abs(nums[m] + nums[n] + curr - target);
            if(tmp < min){
                min = tmp;
                res = nums[m] + nums[n] + curr;
            }

            if(nums[m] + nums[n] + curr < target){
                m++;
            } else {
                n--;
            }
        }
    }
    return res;

    function sorting(a, b){
        if(a > b){
            return 1;
        }else if(a < b){
            return -1;
        }else{
            return 0;
        }
    }
};