Leetcode: 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).

思路： 和3Sum类似，排序后遍历最小值，和右边的值相加，并记录和target最相近的和，此时因为结果只需要得到和，而不是数列，所以不用理会重复元素的情况。

public class Solution {    public int threeSumClosest(int[] num, int target) {        if (num == null || num.length < 3) {            return Integer.MAX_VALUE;        }                Arrays.sort(num);        int res = Integer.MAX_VALUE / 2;        for (int i = 0; i < num.length - 2; i++) {            int second = i + 1, third = num.length - 1;            while (second < third) {                int sum = num[i] + num[second] + num[third];                if (sum == target) {                    return target;                } else if (sum > target) {                        third--;                } else {                        second++;                }                if (Math.abs(target - sum) < Math.abs(target - res)) {                        res = sum;                    }            }        }                return res;            }}