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 ： 跟 3Sum 一样

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        if(num == null || num.length < 3){
            return 0;
        }
        Arrays.sort(num);
        int result = num[0] + num[1]+ num[2];
        for(int i = 0; i< num.length; i++){
            int start = i+1;
            int end = num.length-1;
            while(start < end){
                int tmp = num[i] + num[start]+ num[end];
                if(Math.abs(target - tmp) < Math.abs(target - result))
                    result = tmp;
                if(tmp == target)
                    return tmp;
                else if(tmp < target)
                    start++;
                else 
                    end--;
                
            }
        }
        
        return result;
    }
}