方法①：

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n, sum = 0;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        int num = i;
        while (num > 0)
        {
            if (num % 10 == 0)
            {
                sum++;
                break;
            }
            num /= 10;
        }
    }
    cout << sum;
    return 0;
}

方法②：

#include <bits/stdc++.h>
using namespace std;
int main()
{
    cout << 180;
    return 0;
}

已全部AC。

So easy.

#include <cstdio>
using namespace std;
bool zero(int x){
    while(x>0){
        if(x%10==0)return true;
        x/=10;
    }
    return false;
}
int main(){
    int n,cnt=0;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)if(zero(i))cnt++;
    printf("%d\n",cnt);
    return 0;
}

俗话说得好，暴力出奇迹

#include <iostream>
using namespace std;
int main()
{
	int n, m, num = 0;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		m = i;
		while (m)
		{
			if (m % 10 == 0)
			{
				num++;
				m = 0;
			}
			m /= 10;
		}
	}
	cout << num << endl;
	return 0;
}//代码已AC