题解

#include <bits/stdc++.h>
using namespace std;

vector<pair<int, int>> f(int n, vector<int>& nums) {
    map<int, int> counts;
    for (int i = 0; i < n; i++) {
        counts[nums[i]]++;
    }
    
    vector<pair<int, int>> a(counts.begin(), counts.end());
    sort(a.begin(), a.end(), [](const pair<int, int>& a, const pair<int, int>& b) {
        return a.first < b.first;
    });
    
    return a;
}

int main() {
    int n;
    cin >> n;
    
    vector<int> nums(n);
    for (int i = 0; i < n; i++) {
        cin >> nums[i];
    }
    
    vector<pair<int, int>> result = f(n, nums);
    
    for (const auto& p : result) {
        cout << p.first << " " << p.second << endl;
    }
    
    return 0;
}