leetcode - 3 sum closest

题目来源：http://www.leetcode.com/onlinejudge

解题报告：思路与上题相似

class Solution {
public:

    int min;

    void f(int index, int size, vector &num, int sum, int target)
    {
        if (size == 3)
        {
            if (abs(min) > abs(sum- target))
                min = sum - target;
            return;
            
        }
        if (index == num.size())
            return;


        int i = index;
    
        int next = i+1;
        while(next < num.size() && num[next] == num[i])
            next++;
        f(i+1, size+1, num, sum+num[index], target);
        f(next, size, num, sum, target);

    }
    int threeSumClosest(vector &num, int target) {
        min = 1000000;
        sort(num.begin(),num.end());  
        f(0,0,num,0,target);
        return target + min;
        
    }
};

附录：

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).