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  1. #include <stdio.h>
  2. #include <limits.h>
  3. #define INF UINT_MAX
  4.  
  5. long long unsigned fact(unsigned n)
  6. {
  7.     return n ? n * fact(n-1) : 1;
  8. }
  9.  
  10. unsigned C(unsigned n, unsigned k)
  11. {
  12.     return fact(n)/(fact(k) * fact(n-k));
  13. }
  14.  
  15. unsigned F(unsigned N, unsigned L, unsigned R)
  16. {
  17.     unsigned pos, sum = 0;
  18.     if(R != INF)
  19.     {
  20.         if(L == 0 || R == 0 || N < L || N < R) return 0;
  21.         if(L == 1) return F(N-1, R-1, INF);
  22.         if(R == 1) return F(N-1, L-1, INF);
  23.         for(pos = L; pos <= N-R+1; ++pos)
  24.             sum += C(N-1, pos-1) * F(pos-1, L-1, INF) * F(N-pos, R-1, INF);
  25.     }
  26.     else
  27.     {
  28.         if(L == 1) return fact(N-1);
  29.         for(pos = L; pos <= N; ++pos)
  30.             sum += C(N-1, pos-1) * F(pos-1, L-1, INF) * fact(N-pos);
  31.     }
  32.     return sum;
  33. }
  34.  
  35. int main()
  36. {
  37.     printf("%u\n", F(10,4,3));
  38.     return 0;
  39. }
  40.  
Success #stdin #stdout 0.01s 1720KB
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https://ideone.com/gr8S5
language:
C (gcc 8.3)
created:
12 years ago
visibility:
secret

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