0016._3_Sum_Closest

016. 3Sum Closest

难度: Medium

刷题内容

原题连接

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

内容描述

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

Example:

 Given array nums = [-1, 2, 1, -4], and target = 1.
 
 The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

解题方案

思路
**- 时间复杂度: O(N²)**- 空间复杂度: O(N)**

代码：

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function(nums, target) {
    let result = Infinity;
    let len = nums.length;
    if(len <= 3){
        return nums.reduce((a,b)=>a+b,0);
    }
    nums.sort((a,b)=>a-b);
    for(let k = 0; k<len-2; k++){
        if(k>0 && nums[k-1] === nums[k]){
            continue;
        }
        let i = k + 1;
        let j = len -1;
        while(i<j){
            let count = nums[k] + nums[i] + nums[j];
            if(count === target){
                return target;
            }
            if(Math.abs(result - target) > Math.abs(count - target)){
                result = count;
            }
            if(count > target){
                j--
            }else{
                i ++
            }
        }
    }
    return result;
};