LeetCode OJ：1.Two Sum. FYI: https://yunlinsong.blogspot.com/2019/04/leetcodetwo-sum.html

Two_SumTwoPassHashTable.cpp

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        multimap<int, int> nTable;
        multimap<int, int>::iterator it, cur;
        vector<int> result;
        
        for(int i = 0; i < nums.size(); i++)
            nTable.insert(make_pair(nums[i], i));

        for(cur = nTable.begin(); cur != nTable.end(); cur++) {
            int c = target - cur->first;
            it = nTable.find(c);
            if(it != nTable.end() && cur->second != it->second) {
                if(it->first == cur->first) {
                    result.push_back(it->second);
                    result.push_back(cur->second);
                    return result;
                }
                result.push_back(cur->second);
                result.push_back(it->second);
                return result;
            }
        }
        
        return result;
    }
};