Created
January 7, 2016 00:39
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| def choose(n, k): | |
| """ | |
| A fast way to calculate binomial coefficients by Andrew Dalke (contrib). | |
| """ | |
| if 0 <= k <= n: | |
| ntok = 1 | |
| ktok = 1 | |
| for t in xrange(1, min(k, n - k) + 1): | |
| ntok *= n | |
| ktok *= t | |
| n -= 1 | |
| return ntok // ktok | |
| else: | |
| return 0 | |
| def a(N, P, n): | |
| res = 1 | |
| for i in range(n): | |
| res *= (P-i)/float(N-i) | |
| return res | |
| def f(N, W, B, K, T): | |
| res = choose(K, T) * a(N, W, T) * a(N-T,B,K-T) | |
| #res = choose(K, T) * (float(B)/N)**(K-T) * (float(W)/N)**(T) | |
| print(str(T) + " white balls: " + str(res)) | |
| return res | |
| N = 10 | |
| W = 3 | |
| B = 7 | |
| K = 7 | |
| print(sum([f(N, W, B,K, T) for T in range(0,4)])) |
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