https://oj.leetcode.com/problems/3sum-closest/

Q16.cpp

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        sort(num.begin(), num.end());
        int result = 0, difference = INT_MAX;
        for (size_t i = 0; i < num.size() - 2; i++) {
            size_t begin = i + 1, end = num.size() - 1;
            while (begin < end) {
                int tmp_res = num[i] + num[begin] + num[end];
                int tmp_diff = tmp_res - target;
                if (abs(tmp_diff) < difference) {
                    result = tmp_res;
                    difference = abs(tmp_diff);
                }
                if (tmp_diff < 0) begin++;
                else if (tmp_diff > 0) end--;
                else return tmp_res; // tmp_diff == 0
            }
        }
        return result;
    }
};