leetcode解题方案--016--3 sum closest

题目

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).

分析

这道题比上一道3 sum更简单一点，原因是不用考虑重复的输出。
照例先排序，遍历，设置min为差值的绝对值的最小值。
对于每一个ai，在其后面的数组中用左右指针依次遍历。不断刷新最小值，并将和记为sum。

左右相加较大，则右指针左移，左右相加较小，则左指针右移。

public static int threeSumClosest(int[] nums, int target) {        Arrays.sort(nums);        int min = Integer.MAX_VALUE;        int result = 0;        for (int i = 0; i < nums.length - 2; i++) {            if (min == 0) {                break;            }            int sum = target - nums[i];            for (int lo = i + 1, hi = nums.length - 1; lo < hi; ) {                if (nums[lo] + nums[hi] > sum) {                    if (nums[lo] + nums[hi] - sum < min) {                        min = nums[lo] + nums[hi] - sum;                        result = target+min;                    }                    hi--;                } else if (nums[lo] + nums[hi] < sum) {                    if (sum - nums[lo] - nums[hi] < min) {                        min = sum - nums[lo] - nums[hi];                        result = target-min;                    }                    lo++;                } else {                    min = 0;                    result = target;                    break;                }            }        }        return result;    }