题解 | 泊松分布概率计算器

import math

def poisson_probability(k, lam):
	"""
	Calculate the probability of observing exactly k events in a fixed interval,
	given the mean rate of events lam, using the Poisson distribution formula.
	:param k: Number of events (non-negative integer)
	:param lam: The average rate (mean) of occurrences in a fixed interval
	"""
	# Your code here
	top=math.exp(-lam)*(lam**k)
	val=top/(math.factorial(k))
	return round(val, 5)

if __name__ == "__main__":
    k, lam = map(int, input().split())
    print(poisson_probability(k, lam))