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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).

 思路:遍历第一个数,夹逼后两个数,夹逼的前提是array必须是sorted但。记录最小的和。3sum是要求不重复组合,所以需要加条件跳过,这个并不需要。

public class Solution {    public int threeSumClosest(int[] nums, int target) {    if(nums==null||nums.length<3)    {        return 0;    }    Arrays.sort(nums);    int size=nums.length;    int min=Integer.MAX_VALUE;    int save=0;        for(int i=0;i<=size-3;i++)    {        for(int j=i+1,k=size-1;j<k;)        {               int sum=nums[i]+nums[j]+nums[k];               if(sum==target)               {                   return sum;               }               else if(sum<target)               {                   j++;               }               else               {                   k--;               }               if(Math.abs(sum-target)<min)                {                    min=Math.abs(sum-target);                    save=sum;                }        }    }    return save;    }}                   

 

 

 

16. 3Sum Closest