题解 | #牛牛的排列数#
牛牛的排列数
http://www.nowcoder.com/practice/9ca1c236cdbf46da9e08e1f510808625
def mul(n): if n == 1: return 1 return n * mul(n-1)
a, b = map(int, input().split()) if b > a: print(0) else: print(int(mul(a)/mul(a-b)))
牛牛的排列数
http://www.nowcoder.com/practice/9ca1c236cdbf46da9e08e1f510808625
def mul(n): if n == 1: return 1 return n * mul(n-1)
a, b = map(int, input().split()) if b > a: print(0) else: print(int(mul(a)/mul(a-b)))
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