# How many 0

How many 0

A Benedict monk No. 16 writes down the decimal representations of all natural numbers between and including

m and n , m n

. How many 0's will he write down?

Input consists of a sequence of lines. Each line contains two unsigned 32-bit integers m and n, mn. The last line of input has the value of m negative and this line should not be processed.

For each line of input print one line of output with one integer number giving the number of 0's written down by the monk.

``````10 11
100 200
0 500
1234567890 2345678901
0 4294967295
-1 -1
``````

``````1
22
92
987654304
3825876150
``````

``````#include <stdio.h>
#include <math.h>
#include <string.h>
#include <assert.h>

unsigned countl(char *s){
unsigned r;
if (strlen(s) == 1) return 1;
if (s[0] == '0') {
sscanf(s+1,"%lu",&r);
return 1 + r + countl(s+1);
}
r = pow(10,strlen(s+1));
r += (s[0]-'0') * strlen(s+1) * pow(10,strlen(s+1)-1);
r += countl(s+1);
return r;
}

unsigned count(char *s){
unsigned r = 1; char tmp[20];
if (strlen(s) == 1) return 1;
for (r=0;r<strlen(s)-1;r++) tmp[r] = '9';
tmp[r] = 0;
r = count(tmp);
r += (s[0]-'1') * strlen(s+1) * pow(10,strlen(s+1)-1);
r += countl(s+1);
return r;
}

char x[100], y[100];
unsigned u;

int main(){
while (2 == scanf("%s%s",x,y) && x[0] != '-') {
if (x[0] == '0') printf("%lu\n",count(y));
else {
sscanf(x,"%lu",&u);
sprintf(x,"%lu",u-1);
printf("%lu\n",count(y)-count(x));
}
}
return 0;
}
``````

``````#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
long long dp[10][10];
long long pow(long long a,long long b)
{
long long ret=1;
for(long long i=1; i<=b; i++)
ret*=a;
return ret;
}
long long solve(long long n,long long pos)
{
long long s[15],len = 0,i,tem;
while(n)
{
s[++len] = n%10;
n/=10;
}
s[0] = 0;
long long ans = 0,cnt = 0;
for(i = len; i>=1; i--)
{
if(pos == 0 && i == len)
{
ans+=dp[i-1][pos]*(s[i]-1);
tem = pow(10,i-1)-1;
ans+=solve(tem,0);
}
else
ans+=dp[i-1][pos]*s[i];
ans+=cnt*pow(10,i-1)*s[i];
if(pos)
{
if(s[i]>pos)
ans+=pow(10,i-1);
if(s[i]==pos)
cnt++;
}
else if(i!=len)
{
if(s[i]>pos)
ans+=pow(10,i-1);
if(s[i]==pos)
cnt++;
}
}
return ans+cnt;
}

int main()
{
memset(dp,0,sizeof(dp));
for(long long i=1; i<=9; i++)
{
for(long long j=0; j<=9; j++)
dp[i][j]=dp[i-1][j]*10+pow(10,i-1);
}
long long a,b;
while(scanf("%lld %lld",&a,&b),a+b>=0)
{
long long flag=0;
if(!a)flag = 1;
if(a>b) swap(a,b);
printf("%lld\n",solve(b,0)-solve(a-1,0)+flag);
}
return 0;
}
``````