【LeetCode】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).

解答
题目要求找出数组中三个元素相加的和最接近目标值，然后返回这三个数的值。

先对数组进行排序，然后固定第一个数，第二、三个数在数组前后移动，求出三个数之和，并和目标值比较，判断最接近目标值的三个数的和即可，时间复杂度O(n^2)，代码如下：

public class Solution{
public int threeSumClosest(int[] num,int target){
int min=Integer.MAX_VALUE;
int result=0;

Arrays.sort(num);

int len=num.length;
for(int i=0;i<len;i++){
int j=i+1;
int k=len-1;
while(j<k){
int sum=num[i]+num[j]+num[k];
int diff=Math.abs(sum-target);

if(diff==0){
return sum;
}

if(diff<min){
min=diff;
result=sum;
}
if(sum<=target){
j++;
}else{
k--;
}
}
}
return result;
}
}

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