[LeetCode]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).

思考：类似3Sum。

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int ret=INT_MAX;
		sort(num.begin(),num.end());
		int i,j,k,sum;
		int min=INT_MAX;
		for(i=0;i!=num.size();i++)
		{
			j=i+1;
			k=num.size()-1;
			while(j<k)
			{
				sum=num[i]+num[j]+num[k];
				if(abs(target-sum)<min)
				{
					ret=sum;
					min=abs(target-sum);
				}
				if(sum==target) return target;
				else if(sum<target) j++;
				else k--;
			}
		}
		return ret;
    }
};