16. 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).

1刷
题解：
与3sum类似，先sort，然后首尾夹逼

Time complexity O(n^2), space complexityO(1)

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