1. Two Sum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution.

Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

One C++ version:

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        int m, n, len;
        len = nums.size();
        vector<int> result;
        for(m = 0; m < len - 1; m++){
            for(n=m+1; n < len; n++){
                if(nums[m]+nums[n]==target){
                    result.push_back(m);
                    result.push_back(n);
                    return result;
                }
            }
        }
        return result;
    }
};