题解 | #挑7#
挑7
https://www.nowcoder.com/practice/ba241b85371c409ea01ac0aa1a8d957b
#include <iostream>
#include <string>
using namespace std;
int main() {
int n, sum = 0;
//输入n
cin >> n;
for(int i = 1; i <= n; i++){
if(i % 7 == 0){
sum++;
}else if(to_string(i).find('7') != -1){
sum++;
}
}
cout << sum << endl;
}
// 64 位输出请用 printf("%lld")
to_string(i).find('7') != -1
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查找失败，返回-1
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