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).
这道题和上一道3sum很向，只要稍微改变一下就好了

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        int result = Integer.MAX_VALUE;                    //最后返回的结果
        int distance = Integer.MAX_VALUE;
        Arrays.sort(num);                                 //对数组进行升序排序
        boolean findTarget = false;
        
        for(int i = 0; i < num.length; i++){
            int j = i + 1;
            int k = num.length - 1;                        //双指针
            while(j < k){
                int sum = num[i] + num[k] + num[j];
                if(target == sum){                        //等于target直接返回target的值
                    findTarget = true;
                    result = target;
                    break;
                }
                else if(sum > target){                    //sum比target大k前移,同时更新result,和距离
                    if(Math.abs(sum - target) < distance){
                        distance = Math.abs(sum - target);
                        result = sum;
                    }
                    k--;    
                }
                else{                                    //sum比target小，更新result和距离
                    if(Math.abs(sum - target) < distance){
                        distance = Math.abs(sum - target);
                        result = sum;
                    }
                    j++;
                }
            }
            if(findTarget)
                break;
        }
        
        return result;
    }
}