LeetCode题目一 两数之和

LeetCode题目一 两数之和

#include<iostream>
#include<vector>
#include<unordered_map>
using namespace std;
vector<int> twoSum(vector<int>& nums, int target) {
    vector<int> res;
    for (int i = 0; i < nums.size(); i++){
        for (int j = i + 1; j < nums.size(); j++) {
            if (nums[i]+nums[j] == target) 
            {
                res.push_back(i);
                res.push_back(j);
            }
        }
    }
    return res;
}

vector<int> twoSumHash(vector<int>& nums, int target) {
    vector<int> res;
    unordered_map<int, int> map;

    for (int i = 0; i < nums.size(); i++) {
        map[nums[i]] = i;
    }
    for (int i = 0; i < nums.size(); i++) {
        if ((map.find(target - nums[i]) != map.end())
            && (map[target - nums[i]] != i)) {
            res.push_back(i);
            res.push_back(map[target - nums[i]]);
            return res;
        }
    }  
}

int main()
{
    vector<int> nums;
    vector<int> res;
    nums.push_back(2);
    nums.push_back(7);
    nums.push_back(11);
    nums.push_back(15);
    int target = 9;
    //cout << nums.size()<< endl;
    //res = twoSum(nums, target);
    res = twoSumHash(nums, target);
    for (int i = 0; i < res.size(); i++) {
        cout << res[i];
        cout << " ";
    }
	return 0;
}