题解 | #找出字符串中第一个只出现一次的字符#

#include <iostream>
#include <unordered_map>
#include <vector>
#include <string>
using namespace std;
// 一眼哈希
int main() {
    string str;
    unordered_map<char,int>hashMap;
    vector<char>keys;
    getline(cin,str);
    for(auto ch:str)
    {
        if(hashMap.find(ch) == hashMap.end())
        {
            hashMap[ch] = 1;
            keys.push_back(ch);
        }
        else {
        hashMap[ch]++;
        }
    }
    /*
    for(auto it = hashMap.begin();it!=hashMap.end();++it)
    {
        if(it->second == 1)
        {
            cout << it->first << endl;
            break;
        }
    }
    */
    int i =0;
    for( i = 0;i<keys.size();i++)
    {
        if(hashMap[keys[i]] == 1)
        {
            cout << keys[i] << endl;
            break;
        }
    }
    if(i == keys.size() && hashMap[keys[i]] != 1)
    {
        cout << -1 << endl;
    }
    
}
// 64 位输出请用 printf("%lld")