PAT A1049. Counting Ones (30)

The task is simple: given any positive integer N, you are supposed to count the total number of 1's in the decimal form of the integers from 1 to N. For example, given N being 12, there are five 1's in 1, 10, 11, and 12.

Input Specification:

Each input file contains one test case which gives the positive N (<=2³⁰).

Output Specification:

For each test case, print the number of 1's in one line.

Sample Input:

12

Sample Output:

5

#include <cstdio>#include <algorithm>#include <cstring>#include <string>#define Max 100010using namespace std;int main(){int n,k=1;int m=0;int p,q,r,l;scanf("%d",&n);for(int i=1;i<=n;i++){p=i;while(p!=0){q=p%10;if(q==1) m++;p=p/10;}}printf("%d\n",m);system("pause");return 0;}