CCF-有趣的数（数位DP）

 1 #include <iostream>
 2   
 3   using namespace std;
 4   
 5   int main(){
 6       long long mod = 1000000007;
 7       long long n;
 8       cin>>n;
 9       long long **states = new long long*[n+1];
10     for(long long i =0;i<n+1;i++)
11          states[i]=new long long[6];
12      for(long long i =0;i<6;i++)
13         states[0][i]=0;
14      /*6种状态
15      * 0－－剩013
16     * 1－－剩13
17     * 12－剩01 
18      * 3－－剩3
19      * 4－－剩1
20       * 5－－无
21      */
22      for(long long i=1;i<=n;i++)
23      {
24          long long j = i-1;
25         states[i][0] = 1;
26         states[i][1] = (states[j][0] + states[j][1] * 2) % mod;
27          states[i][2] = (states[j][0] + states[j][2]) % mod;
28          states[i][3] = (states[j][1] + states[j][3] * 2) % mod;
29          states[i][4] = (states[j][1] + states[j][2] + states[j][4] * 2) % mod;
30         states[i][5] = (states[j][3] + states[j][4] + states[j][5] * 2) % mod;
31     }
32      cout<<states[n][5]<<endl;
33      return 0;
34  }