Ural 1586 threeprime numbers (DP)

Subject address: Ural 1586

First, define a prime 3D array to record the prime number. If I * 100 + J * 10 + K is a prime number, Mark prime [I] [J] [k] as 1, otherwise, the value is 0. in this way, the subsequent processing is very convenient.

Then define a three-dimensional DP array. DP [N] [I] [J] indicates the number of prime numbers when the ten digits of the current N bits are I and the single digit is J, at this time, the State needs to be transferred from prime [k] [I] [J] to prime number, so the state transition equation is:

If (prime [J] [k] [H]) DP [I] [k] [H] + = DP [I-1] [J] [k]

The Code is as follows:

#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <stdlib.h>#include <math.h>#include <ctype.h>#include <queue>#include <map>#include <set>#include <algorithm>using namespace std;const int mod=1e9+9;int prime[11][11][11], dp[10001][10][10];int main(){    int i, j, k, n, h, x, flag, sum;    memset(prime,0,sizeof(prime));    memset(dp,0,sizeof(dp));    for(i=1; i<=9; i++)    {        for(j=0; j<=9; j++)        {            for(k=1; k<=9; k++)            {                x=i*100+j*10+k;                flag=0;                for(h=2; h<=sqrt(x); h++)                {                    if(x%h==0)                    {                        flag=1;                        break;                    }                }                if(!flag)                    prime[i][j][k]=1;                dp[3][j][k]+=prime[i][j][k];            }        }    }    scanf("%d",&n);    for(i=4;i<=n;i++)    {        for(j=0;j<=9;j++)        {            for(k=0;k<=9;k++)            {                for(h=0;h<=9;h++)                {                    if(prime[j][k][h])                    {                        dp[i][k][h]+=dp[i-1][j][k];                        dp[i][k][h]%=mod;                    }                }            }        }    }    sum=0;    for(i=0;i<=9;i++)    {        for(j=0;j<=9;j++)        {            sum+=dp[n][i][j];            sum%=mod;        }    }    printf("%d\n",sum);    return 0;}

Ural 1586 threeprime numbers (DP)