代码如下：

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

int main() {
    long long n;
    cin >> n;
    
    vector<long long> a(n);  
    vector<long long> b(1000001, 0);
    
    for (long long i = 0; i < n; i++)
        cin >> a[i];
    
    for (long long i = 0; i < n; i++) {
        b[a[i]]++;  
    }
    
    auto max_element_ptr = max_element(a.begin(), a.end());  
    
    for (long long i = 1; i <= *max_element_ptr; i++) {
        if (b[i] != 0) {
            cout << i << " " << b[i] << endl;
        }
    }
    
    return 0;
}

本地运行没问题，但提交上去就全部RE了