#include<cstdio>
#define IOFileName "P1848"
int n,m,x,y,ans=0;
int main(){
//freopen(IOFileName".in","r",stdin);
//freopen(IOFileName".out","w",stdout);
scanf("%d %d\n",&n,&m);
for(int i=1;i<=n;i++){
x=i;
while(x!=0){
y=x%10;
x/=10;
if(y==m){
ans++;
}
}
}
printf("%d\n",ans);
}

#include <iostream>
using namespace std;
int x,r,l,k,ans;
int main(){
cin>>r>>x;
for(l=1;l<=r;l++)
{
k=l;
while(k!=0){if(k%10==x)ans++;k/=10;}
}
cout<<ans;
return 0;
}

program _1848jishu2;
label 00,01;
var a:integer;
ifactor,count,n,low,curr,high:int64;
begin
read(n,a);
ifactor:=1;
if a<>0 then
begin
while(n div ifactor<>0) do
begin
low:=n-(n div ifactor)*ifactor;
curr:=(n div ifactor)mod 10;
high:=n div(ifactor*10);
if curr<=a then
if curr<a then begin inc(count,high*ifactor);goto 00;end
else begin inc(count,high*ifactor+low+1);goto 00;end
else begin inc(count,(high+1)*ifactor);goto 00;end;
00:ifactor:=ifactor*10;
end;
end
else
begin
ifactor:=10;
count:=n div 10;
while (n div ifactor<>0) do
begin
low:=n-(n div ifactor)*ifactor;
curr:=(n div ifactor)mod 10;
high:=n div(ifactor*10);
if high=0 then break;
if curr=0 then begin inc(count,(high-1)*ifactor+low+1);goto 01;end
else begin inc(count,high*ifactor);goto 01;end;
01:ifactor:=ifactor*10;
end;
end;
writeln(count);
readln;
end.
这才是数学方法= =

数学方法，瞬间全过！！！！
试一试一瞬间刷爆int64没问题！！！！

function p(x,y:longint):int64;begin p:=round(exp(y*ln(x))) end;
var a:array[0..11]of int64; i,j,k,l:longint; s:string;
begin
readln(a[10],a[11]);
str(a[10],s);
for i:=1to ord(s[0])do
begin
for j:=1to ord(s[0])-i do
begin
for k:=0to 9do
a[k]:=a[k]+(ord(s[i])-ord('0'))*p(10,ord(s[0])-i-1);
end;

for j:=1to ord(s[i])-ord('0')-1do
a[j]:=a[j]+p(10,ord(s[0])-i);

a[ord(s[i])-ord('0')]:=
a[ord(s[i])-ord('0')]+a[10]mod p(10,ord(s[0])-i)+1
end;
for i:=1to ord(s[i])do if s[i]='0'then a[0]:=a[0]-p(10,ord(s[0])-i);
writeln(a[a[11]]);
end.

var s,n,x,i:longint;

procedure jishu(a:longint);
var b:longint;
begin
while a<>0 do
begin
b:=a mod 10;
if b=x then s:=s+1;
a:=a div 10;
end;
end;

begin
s:=0;
read(n);
read(x);
for i:=1 to n do
jishu(i);
writeln(s);
end.

Vijos 题解：http://hi.baidu.com/umule/item/2c997f8ed9600fdae596e017
有疑问请留言 共同进步

代码:

var
a,x,j,i,total:longint;
s:string;
begin
readln(a,x);
for i:=1 to a do
begin
str(i,s);
for j:=1 to length(s) do
if s[j]=chr(ord('0')+x) then inc(total);
end;
write(total);
end.

#include <stdio.h>
int main()
{
int n,x,a,b=0,c;
scanf ("%d%d",&n,&x);

for (c=1;c<=n;c++)
{

a=c;
while (a)
{
if (a%10==x)
b++;
a/=10;
}
}
printf ("%d",b);
return 0;
}

var n,m,i,j,x:longint;
s,c:string;
begin
assign(input,'count.in');
reset(input);
read(n);
read(x);
close(input);
m:=0;
for i:=1 to n do
begin
str(i,s);
str(x,c);
if pos(c,s)=0 then
continue;
for j:=1 to length(s) do
if s[j]=c then
inc(m);
end;
assign(output,'count.out');
rewrite(output);
write(m);
close(output);
end.

include <cstdio>

using namespace std;
int main()
{
int n,k,ans=0;
scanf("%d%d",&n,&k);
for(int i=1;i<=n;i++)
{
for(int j=i;j>0;j/=10)
if(j%10==k)ans++;
}
printf("%d",ans);
return 0;
}
新学C+=的

为什么错？？？？

var
n,i,t,sum:longint;
x:integer;
s,s1:string;
begin
read(n,x);
for i:=1 to n do
begin
str(i,s1);
s:=s+s1;
end;
for i:=1 to length(s) do
begin
val(s[i],t);
if t=x then sum:=sum+1;
end;
write(sum);
end.

a[i]=a[i/10]+1 (i mod 10=x)
a[i]=ai/10
递推累加即可

var
n,x,j,ans:longint;
s,z:string;
begin
readln(n,x);
str(x,z);
for j:=1 to n do
begin
str(j,s);
while pos(z,s)<>0 do
begin
ans:=ans+1;
s[pos(z,s)]:=' ';
end;
end;
writeln(ans);
end.

#include<cstdio>
using namespace std;
int main()
{
freopen("count.in","r",stdin);
freopen("count.out","w",stdout);
int ans=0,n,k,sb;
scanf("%d%d",&n,&k);
for(int i=1;i<=n;i++){int j=i;
while(j>0){sb=j%10;if(sb==k)ans++;j/=10;}
}printf("%d\n",ans);
return 0;
}

#include<iostream>
#include<string.h>
using namespace std;
int main(){
int i,j,k,n,m;
cin>>n>>m;
for(i=1,k=0;i<=n;i++){
j=i;
while (j>0){
if(j%10==m)k++;
j/=10;
}
}
cout<<k<<"\n";

return 0;
}
直接AC

用比赛的源程序，忘删文抄了

#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;
int main()
{
int n,x,a,ans=0;
scanf("%d%d",&n,&x);
for(int i=1;i<=n;i++){
int j=1,a=i;
while(a!=0){
if(a%10==x) ans++;
a/=10;
}
}
printf("%d",ans);
return 0;
}

#include<iostream>
using namespace std;
int main(){
int n,x,sum=0;
cin>>n>>x;
for(int i=1;i<=n;i++){
int t=i;
while(t>0){
if(t%10==x) sum++;
t/=10;
}
}
cout<<sum<<endl;
return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
int n = 0;
int x = 0;
scanf("%d%d", &x, &n);
int i = 0;
int num = 0;
for (i = 1; i <= n; i++)
{
int j = i;
while (j)
{
if (j % 10 == x)
{
num++;
}
j = j / 10;
}

}
printf("%d\n", num);
return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
int n = 0;
int x = 0;
scanf("%d%d", &x, &n);
int i = 0;
int num = 0;
for (i = 1; i <= n; i++)
{
int j = i;
while (j)
{
if (j % 10 == x)
{
num++;
}
j = j / 10;
}

}
printf("%d\n", num);
return 0;
}