3Sum Closest

3Sum Closest

问题：

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.

思路：

　　典型的双指针问题

我的代码：

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