题解 | #挑7#
挑7
https://www.nowcoder.com/practice/ba241b85371c409ea01ac0aa1a8d957b
#include <iostream>
using namespace std;
int foo(int x){
if(x<7) return 0;
if(x%10==7) return 1;
else return foo(x/10);
}
int main(){
int n,res = 0;
cin >> n;
for(int i =0; i<=n ; i++){
if(i%7==0) res += 1;
else res += foo(i);
}
cout << res-1;
}
