progs/a869.py


1
2
3
4
5
6
7
8
9
10
11
12
13

def permutation_coefficient(n, k): 
	P = [[0 for i in range(k + 1)] 
			for j in range(n + 1)] 
	for i in range(n + 1): 
		for j in range(min(i, k) + 1): 
			if (j == 0): 
				P[i][j] = 1
			else: 
				P[i][j] = P[i - 1][j] + ( 
						j * P[i - 1][j - 1]) 
			if (j < k): 
				P[i][j + 1] = 0
	return P[n][k]