Java [leetcode 16] 3Sum Closest

题目描述：

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).

解题思路：

这个跟3Sum的思路差不多，不过实现的过程就简单多了。外面一个大的循环，里面也是从两边开始，如果三个数之和减去目标值的绝对值较小，则更新之并记录此三个数之和。

代码如下：

 1 public class Solution {
 2     public int threeSumClosest(int[] nums, int target) {
 3         int length = nums.length;
 4         int min = Integer.MAX_VALUE;
 5         int left, right, comp, result = 0;
 6
 7         if (length < 3)
 8             return 0;
 9         Arrays.sort(nums);
10
11         for (int i = 0; i < length - 2; i++) {
12             left = i + 1;
13             right = length - 1;
14             while (left < right) {
15                 comp = nums[i] + nums[left] + nums[right];
16                 if (Math.abs(comp - target) < min){
17                     min = Math.abs(comp - target);
18                     result = comp;
19                 }
20                 if (comp > target)
21                     right--;
22                 else if (comp < target)
23                     left++;
24                 else
25                     return target;
26             }
27         }
28         return result;
29     }
30 }

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).