hdu3652 A-B number 数位DP

题目描述

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.

大意

找一个数使它包含13并且整除13。很明显的数位DP，四维数组记录【当前位置】【余数】【这一位的情况】【操作】。

代码

#include<cstdio>  #include<cstring>  #include<algorithm>  using namespace std;  int n;  int dp[10][15][2][10],a[10];  int dfs(int pos,int mod,int t,int pre,int limit)  {      if (pos==-1)return (mod==0&&t);      if (!limit&&dp[pos][mod][t][pre]!=-1) return dp[pos][mod][t][pre];      int up=limit?a[pos]:9;      int ans=0;      for(int i=0;i<=up;++i)      {          ans+=dfs(pos-1,(mod*10+i)%13,t||(pre==1&&i==3),i,limit&&(i==up));      }      if (!limit) dp[pos][mod][t][pre]=ans;      return ans;  }  int solve(int x)  {      int len=0;      while(x)      a[len++]=x%10,x/=10;      return dfs(len-1,0,0,0,1);  }  int main()  {       memset(dp,-1,sizeof(dp));      while(scanf("%d",&n)!=EOF)      {          printf("%d\n",solve(n));      }      return 0;  }