HDU 3652 B-number 数位dp

G - B-number
Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u
Submit Status Practice HDU
3652

Appoint description: 
System Crawler  (2016-04-22)

Description

A wqb-number, or B-number for short, is a non-negative integer whose decimal form contains the sub- string "13" and can be divided by 13. For example, 130 and 2613 are wqb-numbers, but 143 and 2639 are not. Your task is to calculate
how many wqb-numbers from 1 to n for a given integer n.
 

Input

Process till EOF. In each line, there is one positive integer n(1 <= n <= 1000000000).
 

Output

Print each answer in a single line.
 

Sample Input

13
100
200
1000

 

Sample Output

1
1
2
2

 数位dp flag表示状态 mod判断是否能整除
ACcode：

#include <iostream>
#include <cstdio>
#include <cstring>
#define ll long long
using namespace std;
int dp[25][25][3];
int date[25];
int dfs(int pos,int mod,int flag,bool limit){
if(!pos)return mod==0&&flag==2;
if(!limit&&dp[pos][mod][flag]!=-1)return dp[pos][mod][flag];
int ret=0;
int ed=limit?date[pos]:9;
for(int i=0;i<=ed;i++){
int tmp=flag;
int modd=(mod*10+i)%13;
if(flag==1&&i==3)
tmp=2;
else if(flag==0&&i==1)
tmp=1;
else if(flag==1&&i!=1&&i!=3)
tmp=0;
ret+=dfs(pos-1,modd,tmp,limit&&i==ed);
}
return limit?ret:dp[pos][mod][flag]=ret;
}
void doit(int n){
int len=0;
while(n){
date[++len]=n%10;
n/=10;
}
printf("%d\n",dfs(len,0,0,1));
}
int main(){
int n;memset(dp,-1,sizeof(dp));
while(~scanf("%d",&n))doit(n);
}