leetcode1-two-sum_method3_hashmap2.cpp

#include<iostream>
#include<unordered_map>
#include<vector>
using namespace std;

class Solution {
public:
    vector<int> twoSum(vector<int> &nums, int target)
    {
        unordered_map<int, int> dict;
        vector<int> res(2,-1);
        for (int i = 0; i < nums.size(); i++)
        {
            int query = target - nums[i];
            if (dict.find(query) == dict.end())
                dict[nums[i]] = i; // map映射: value->index
            else
            {
                res[1] = i;
                res[0] = dict[query];
                return res;
            }
        }
        return {};
    }
};
// 下面是测试
int main()
{
    Solution sol;
    vector<int> arr = {3, 2, 4};
    vector<int> res = sol.twoSum(arr, 7);
    for (int i : res)
        printf("%d ", i);
    return 0;
}