【Codeforces441E】Valera and Number [DP]

Valera and Number

Time Limit: 20 Sec  Memory Limit: 512 MB

Description

　　

Input

　　

Output

　　

Sample Input

　　5 3 25

Sample Output

　　1.9218750000

HINT

　　

Solution

　　考虑运用DP。

　　

Code

 #include<iostream>
 #include<string>
 #include<algorithm>
 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<cmath>
 using namespace std;
 typedef long long s64;

 const int ONE = ;
 const int MOD = 1e9 + ;
 const int all = ;

 int x, n;
 double p;
 double f[][][][];
 double Ans;
 int val, num;

 int get()
 {
         int res;char c;
         while( (c=getchar())< || c> );
         res=c-;
         while( (c=getchar())>= && c<= )
         res=res*+c-;
         return res;
 } 

 void Deal_first(int n)
 {
         int record[], num = , x = n;
         while(x)
             record[++num] = x & ,
             x >>= ;
         int j = , pos = , val = record[pos];
         for(pos = ; pos + j -  <= num; j++)
             if(record[pos + j] != val) break;

         f[][n & all][j][val] = ;
 }

 int Get(int x)
 {
         int res = ;
         while(x %  == ) res++, x >>= ;
         return res;
 }

 int main()
 {
         x = get(), n = get(), p = (double)get() / ;
         Deal_first(x);

         for(int i = ; i < n; i++)
             for(int s = ; s <= all; s++)
                 for(int j = ; j <= ; j++)
                     for(int k = ; k <= ; k++)
                     {
                         val = s >>  -  & ;
                         if(val != k) num = ; else num = j + ;
                         f[i + ][s <<  & all][num][val] += f[i][s][j][k] * p;

                         val = s == all ? (k ^ ) : k;
                         if(val != k && k == ) num = ; else num = j;
                         f[i + ][s +  & all][num][val] += f[i][s][j][k] * ( - p);
                     }

         for(int s = ; s <= all; s++)
             for(int j = ; j <= ; j++)
                 for(int k = ; k <= ; k++)
                 {
                     if(s ==  && k == ) val = j + ;
                     else if(s ==  && k == ) val = ;
                     else val = Get(s);
                     Ans += f[n][s][j][k] * val;
                 }

         printf("%.8lf", Ans);
 }

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