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].

Answer:

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> result;
        int m_count = nums.size();
        int m_target = target;
        
        if (m_count < 2){
            return result;
        }
        
        if (m_count == 2){
            if((nums[0] + nums[1]) == target)
            {
                result.push_back(0);
                result.push_back(1);
                return result;
            }
            else{
                return result;
            }
        }
        
        int m_min = nums.at(0);
        int m_max = nums.at(0);
        
        for (int index = 1;index < m_count;index++){
            if(nums[index] > m_max){
                m_max = nums[index];
                continue;
            }
            if(nums[index] < m_min){
                m_min = nums[index];
            }
        }
        
        map<int,map<string,int>> m_flagMap;
        
        for (int index = 0;index < m_count;index++){
            m_flagMap[nums[index]]["bool"] = 1;
            m_flagMap[nums[index]]["count"] ++;
            m_flagMap[nums[index]]["index"] = index;
        }
        
        for (int index = 0;index < m_count;index++){
            int m_sub = m_target - nums[index];
            map<string,int> indexMap = m_flagMap[m_sub];
            if(indexMap["bool"] == 1 && indexMap["index"] != index){
                result.push_back(index);
                result.push_back(indexMap["index"]);
                break;
            }
        }
        
        return result;
    }
};