题目描述

代码：

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

int main(){
	int n;
	cin>>n;
	int A[n];
	for(int i = 0; i < n; i++){
		cin>>A[i];
	}
	sort(A,A+n);
	int slow = 0,fast = 0;
	while(fast < n){
		if(slow != fast){
			A[slow] = A[fast];
		}
		if(fast == n-1){
			break;
		}
		if(A[fast + 1] != A[fast]){
			slow++;
		}
		fast++;
	}
	cout<<slow+1<<endl;
	for(int i = 0; i <= slow; i++){
		cout<<A[i]<<" ";
	}
	return 0;
}