使用了两层循环:

class Solution {
public:
    /**
     * 
     * @param numbers int整型vector 
     * @param target int整型 
     * @return int整型vector
     */
    vector<int> twoSum(vector<int>& numbers, int target) {
        // write code here
        // 最简单的应该是 o(n^2) 了
        int i = 0; 
        int j = 1;
        for(;i<numbers.size() - 1; ++i){
            for(j = i+1;j<numbers.size(); ++j){
                if(numbers[i] + numbers[j] == target) {
                    return {i+1,j+1};
                }
            }
        }
        return {i+1,j+1};
    }
};