用函数，不迷路！

已AC，请放心食用

#include <iostream>
using namespace std;
int six(int n)
{
    int x = n;
    bool f = false;
    while (x > 0)
    {
        if (x % 10 == 6)
        {
            f = true;
            break;
        }
        x /= 10;
    }
    return f;
}
int main()
{
    int n, num = 0;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        if (six(i))
        {
            num++;
        }
    }
    if (num % 2 == 1)
    {
        cout << "library";
    }
    else
    {
        cout << "playground";
    }
    return 0;
}

养成好习惯，看后点个赞😎！

没人发，我来

#include<bits/stdc++.h>
using namespace std;
int n,a[1005],sum,num;
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        int m=i;
        while(m>0)
        {
            if(m%10==6)
            {
                sum++;
                break;
            }
            m/=10;
        }
    }
    if(sum%2==0)
    {
        cout<<"playground";
    }
    else
    {
        cout<<"library";
    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n, m, k = 0;
	cin >> n;
	for (int i = 1; i <= n; i++){
		m = i;
		//短除法判断各个位是否有等于6
		while(m > 0){
			if(m%10 ==6){
				k++;//计数器
				break; 
			}
			m /= 10;
		} 
	}
	//判断含有6的数字的个数是奇数还是偶数
	//是奇数，就去图书馆，否则就去游乐场
	if(k % 2 == 0){
		cout << "playground";
	} else {
		cout << "library";
	}
	return 0;
}