3Sum Closest

3Sum Closest是3Sum的變種

要求找到最接近的那個結果

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 package com.rust.cal;
 2 
 3 import java.util.Arrays;
 4 
 5 public class ThreeSumClosest {
 6     public static int threeSumClosest(int[] nums, int target) {
 7         if (nums.length < 3) {
 8             return -1;
 9         }
10         int closest = Math.abs(nums[0] + nums[1] + nums[2] - target);//find distance
11         Arrays.sort(nums);
12         int len = nums.length;
13         int res = 0;//nums[0] + nums[1] + nums[2];
14         for (int i = 0; i < len-2; i++) {
15             if (i > 0 && nums[i] == nums[i-1]) continue;//skip this loop
16             int l = i + 1;
17             int r = len - 1;
18             while (l < r) {
19                 int sum = nums[l] + nums[r] + nums[i];
20                 if (closest >= Math.abs(sum-target)) {
21                     closest = Math.abs(sum-target);
22                     res = sum;
23                 }
24                 if (sum == target) {
25                     return sum;
26                 } else if (sum - target > 0) {
27                     r--;
28                 } else {
29                     l++;
30                 }
31             }
32         }
33         return res;
34     }
35 
36     public static void main(String args[]){
37         int[] nums = {1,2,-10,2,2,0,3,5,5,-5,-6,0};
38         int[] nums1 = {1,1,1};
39         System.out.println(threeSumClosest(nums,0));
40     }
41 }      

設立左右兩個遊标，每次得到結果都和最接近的closest比較一下