A1049. Counting Ones (30)

1049. Counting Ones (30)

时间限制

10 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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>
int main(){
int n,a = 1,sum = 0;
scanf("%d",&n);
int now,left,right;    //当前位数，左边数字，右边数字
while(n/a){
left = n/(a*10);
now = n/a%10;
right = n%a;
if(now==0){
sum += left*a;
}
else if(now==1){
sum += left*a+right+1;
}
else
sum += (left+1)*a;
a *= 10;
}
printf("%d\n",sum);
return 0;
}