leetcode--3Sum Closest

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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).

public class Solution {    public int threeSumClosest(int[] num, int target) {        int sum = 0, length = num.length;if(length > 0) {if(length <= 3) {for(int i = 0; i < length; ++i)sum += num[i];}else {Arrays.sort(num);int difference = Integer.MAX_VALUE;for(int i = 0; i < length; ++i) {int start = i + 1, end = length - 1;while(start < end){int temp = num[i] + num[start] + num[end];if(temp == target) return target;else {if(difference > Math.abs((target - temp))){sum = temp;difference = Math.abs((target - temp));}if(temp < target)++start;else--end;}}}}}return sum;        }}