Online judge for leetcode

Question 1: Two Sum

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> res;
        vector<int>::size_type index1, index2;
        
        for (index1 = 0; index1 < numbers.size() - 1; index1++) {
            for (index2 = index1 + 1; index2 < numbers.size(); index2++) {
                if (numbers[index1] + numbers[index2] == target) {
                    res.push_back(index1 + 1);
                    res.push_back(index2 + 1);
                    return res;
                }
            }
        }
    }
};