[leetcode]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).


思路：

这道题跟[leetcode]3Sum并没有太大差别，甚至比更简单，因为并不需要再关心重复数组了，只需要维护一个最小值即可。

代码如下：

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        int length = num.length;
        int min = Integer.MAX_VALUE;
        int result = 0;
        Arrays.sort(num);
        for(int i = 0; i < length - 2;i++){
            int begin = i + 1;
            int end = length - 1;
            while(begin < end){
                if(Math.abs(num[i] + num[begin] + num[end] - target) < min){
                    min = Math.abs(num[i] + num[begin] + num[end] - target);
                    result = num[i] + num[begin] + num[end];
                }
                if(num[i] + num[begin] + num[end] > target) end--;
                else if(num[i] + num[begin] + num[end] < target) begin++;
                else return target;
            }
        }
        return result;
    }
}

　还是要记得排序，求和问题中，排序似乎是很有效的。