题解

话不多说，上题解：

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n,sum = 0,value;
    int a[1000000] = {0};
    cin >> n;              
    for(int i = 0;i < n;i++){
        cin >> value;                                                                                           
        if(a[value] == 0){
            a[value] = 1;
            sum++;
        }
    }
    cout << sum;
    return 0;
}