1041 be unique (20 points (s)) (hash: find the first number that occurs once)

title

Ideas

Two things are needed ： One is a table that records the sequence , One is a table that records the number of times

Code

#include <iostream>
using namespace std;
int hashtable[100100], num[100100];
#define rep(i,j,k) for(int i=j;i<k;i++)
int main() {
    
	int n;
	cin >> n;
	rep(i, 0, n) {
    
		cin >> num[i];
		hashtable[num[i]]++;
	}
	rep(i, 0, n) 
		if (hashtable[num[i]] == 1) {
    
			cout << num[i];
			return 0;
		}
	cout << "None";
}

doubt

I don't know why I'm wrong ╮（╯＿╰）╭

using namespace std;
#include <unordered_map>
#define rep(i,j,k) for(int i=j;i<k;i++)
#include <iostream>
int main() {
    
	unordered_map<int, int>bets;
	int n, temp;
	cin >> n;
	rep(i, 0, n) {
    
		cin >> temp;
		bets[temp]++;
	}
	for (auto i : bets) {
    
		//cout << i.second << endl;
		if (i.second == 1) {
    
			cout << i.first;
			return 0;
		}
	}
	cout << "None";
	return 0;
}