leetcode 16. 3Sum Closest

题目

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
和3Sum 不同的地方在于用一个阈值存储最小间隔

代码

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