LeetCode 3Sum Closest

原题链接在这里：https://leetcode.com/problems/3sum-closest/

与3Sum类似，这里不用去掉重复的值，因为这里不需要避免存入重复的值。

基本思路就是维护一个最小的diff，排序之后夹逼。 

Time Complexity: O(n^2), sort takes O(n*logn), for loop 中的每一个 i 后的while loop 用了O(n) time.

Space Complexity is O(1).

 

AC Java:

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