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).

LeetCode-3Sum Closest

C++:
class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int ret;
        int temp=INT_MAX;
        sort(num.begin(),num.end());
        for(int i=0;i<num.size()-2;i++){
            int j=i+1;
            int k=num.size()-1;
            while(j<k){
                int sum=num[i]+num[j]+num[k];
                if(abs(sum-target)<temp){
                    ret=sum;
                    temp=abs(sum-target);
                }
                if(sum>target) k--;
                else j++; 
            }
        }
        return ret;
    }
};
Java:
public class Solution {
    public int threeSumClosest(int[] num, int target) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int ret=0;
        int temp=Integer.MAX_VALUE;
        Arrays.sort(num);
        for(int i=0;i<num.length-2;i++){
            int j=i+1;
            int k=num.length-1;
            while(j<k){
                int sum=num[i]+num[j]+num[k];
                if(Math.abs(sum-target)<temp){
                    ret=sum;
                    temp=Math.abs(sum-target);
                }
                if(sum>target) k--;
                else j++;
            }
        }
        return ret;
    }
}