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：
思路和3Sum类似，只需添加判断是否是最近的即可。
代码：

    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 cur = INT_MAX, res;
        int len = num.size();
        int i,j,k;
        sort(num.begin(), num.end());
        for(i = 0; i < len-2; i++){
            while(i > 0 && num[i] == num[i-1])
                i++;
            j = i+1;
            k = len - 1;
            while(j < k){
                int t = num[i]+num[j]+num[k];
                if(t<target)
                    j++;
                else if(t>target)
                    k--;
                else{
                    return target;
                }
                if(abs(t-target) < cur){
                    cur = abs(t-target);
                    res = t;
                }
            }
        }
        return res;
    }