题解 | #挑7#

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

int main() {
    int n;
    cin >> n;
    regex regex_pattern("\\d*[7]\\d*");
    vector<int> res;
    int count = 0;
    for(int i = 7; i <= n; ++i){
        if(i % 7 == 0){
            count++;
            res.push_back(i);
        }else if(regex_match(to_string(i),regex_pattern)){
            count++;
            res.push_back(i);
        }
    }
    // for(auto &i : res){
    //     cout << i << " ";
    // }
    cout << count << endl;
}
// 64 位输出请用 printf("%lld")