题解 | 两数之和

#include <unordered_map>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param numbers int整型vector 
     * @param target int整型 
     * @return int整型vector
     */
    vector<int> twoSum(vector<int>& numbers, int target) {
        // write code here
        vector<int> res;
        if(numbers.size()==0)
        {
            return res;
        }
        unordered_map<int, int> hash;//(key,value)=(numbers[i],i)3 0  4 1 
        for(int i=0;i<numbers.size();i++)
        {
            int x = target -numbers[i];
            if(hash.count(x))
            {
                res.push_back(hash[x]);
                res.push_back(i+1);
            }
            else {
             hash[numbers[i]]=i+1;
            }
        }
        return res;
    }
};