C++ :

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

int a[110],n,x,c;
int i;
int main() {
	cin>>n;
	for(i = 0;i < n;i++){
		cin>>x;
		if(a[x] == 0) c++;
		a[x]++;
	}
	
	cout<<c<<endl;
	for(i = 1;i <= 100;i++){
		if(a[i] != 0){
			cout<<i<<" "<<a[i]<<endl;
		}
	}
}

Java :

import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int j = 0;
		int[] a = new int[101];
		for (int i = 0; i < n ; i++) {
			int x = sc.nextInt();
			if(a[x]==0)
				++j;
			a[x]++;
		}
		System.out.println(j);
		for(int i = 1 ; i < 101 ; i++)
		{
			if(a[i]>0)
			System.out.println(i+" "+a[i]);
		}
	
	}
}

Python :

n = int(input())
a = input().split()
t = 0
k = 0
# b[1]记录1出现的次数,b[2]记录2出现的次数...b[100]记录100出现的次数,因为b[0]没有用到,所以[0]*101,而不是100
b = [0] * 101
# 类型转换,把字符串列表a转换成整型列表a
for i in range(0, n):
    a[i] = int(a[i])
    k = a[i]
    b[k] += 1
# 遍历b列表,输出一共的发言人数
for i in range(1, 101):
    if b[i] > 0:
        t += 1
# 输出发言人数
print(t)
# 再次遍历b列表,输出发言人学号和发言次数,i表示学号,b[i]表示次数
for i in range(1, 101):
    if b[i] > 0:
        print(i, b[i])