yunyin/birthday.py

#coding=utf-8
'''
Created on 2017年6月9日
@vsersion:python3.6
@author: liuyuqi
'''
from scipy.special import comb, perm
from math import factorial
#1-C(365,n)n!/(365)^n
init=365;
k=0;
for n in range(4,init):
    pk=1-comb(365,n)*factorial(n)/pow(365,n);
    if pk>=0.5 :
        k=n;
        break;
print(k)
# perm(m, n) 排列数
# comb(3, 2) 组合数
# pow(a,b) n次方
# factorial (x)阶乘