Submission #19203

# Submission time Handle Problem Language Result Execution time Memory
19203 2016-02-20T15:32:31 Z kriii Ω (kriii4_P3) C++14
0 / 100
0 ms 1084 KB
#include <stdio.h>
  
const long long mod = 1000000007;
  
long long fpow(long long a, long long p)
{
    a = (a % mod + mod) % mod;
    p = (p % (mod - 1) + mod - 1) % (mod - 1);
    long long r = 1;
    while (p){
        if (p & 1) r = r * a % mod;
        a = a * a % mod;
        p >>= 1;
    }
    return r;
}
  
int main()
{ 
    int P,Q,N,K; scanf ("%d %d %d %d",&P,&Q,&N,&K);
  
    if (K == 0) puts("0");
    else if (K == N) puts("1");
    else if (Q == 0) puts("1");
    else if (Q == P) puts("0");
    else if (Q * 2 == P) printf ("%lld\n",K*fpow(N,-1)%mod);
    else{
        long long v[101];
        long long pr = Q * fpow(P,-1), rv = fpow(1-pr,-1);
        v[0] = 0; v[1] = 1;
        for (int i=2;i<=N;i++) v[i] = ((v[i-1] - pr * v[i-2]) * rv % mod + mod) % mod;
        printf ("%lld\n",v[K]*fpow(v[N],-1)%mod);
    }
  
    return 0;
}
# Verdict Execution time Memory Grader output
1 Correct 0 ms 1084 KB Output is correct
2 Correct 0 ms 1084 KB Output is correct
3 Correct 0 ms 1084 KB Output is correct
4 Correct 0 ms 1084 KB Output is correct
5 Correct 0 ms 1084 KB Output is correct
6 Correct 0 ms 1084 KB Output is correct
7 Correct 0 ms 1084 KB Output is correct
8 Correct 0 ms 1084 KB Output is correct
9 Correct 0 ms 1084 KB Output is correct
10 Correct 0 ms 1084 KB Output is correct
11 Correct 0 ms 1084 KB Output is correct
12 Correct 0 ms 1084 KB Output is correct
13 Incorrect 0 ms 1084 KB Output isn't correct
14 Halted 0 ms 0 KB -