main3.cpp

/// Source : https://leetcode.com/problems/two-sum/description/
/// Author : liuyubobobo
/// Time   : 2017-11-15

#include <iostream>
#include <vector>
#include <cassert>
#include <unordered_map>

using namespace std;

/// One-Pass Hash Table
/// Time Complexity: O(n)
/// Space Complexity: O(n)
class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {

        unordered_map<int,int> record;
        for(int i = 0 ; i < nums.size() ; i ++){

            int complement = target - nums[i];
            if(record.find(complement) != record.end()){
                int res[] = {i, record[complement]};
                return vector<int>(res, res + 2);
            }

            record[nums[i]] = i;
        }

        throw invalid_argument("the input has no solution");
    }
};


void printVec(const vector<int>& vec){
    for(int e: vec)
        cout << e << " ";
    cout << endl;
}

int main() {

    const int nums[] = {0,4,3,0};
    vector<int> nums_vec( nums, nums + sizeof(nums)/sizeof(int) );
    int target = 0;
    printVec(Solution().twoSum(nums_vec, target));

    return 0;
}