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053.py
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executable file
·34 lines (25 loc) · 737 Bytes
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#!/usr/bin/python
# -*- coding: utf-8 -*-
#There are exactly ten ways of selecting three from five, 12345:
#123, 124, 125, 134, 135, 145, 234, 235, 245, and 345
#In combinatorics, we use the notation, 5C3 = 10.
#In general,
#nCr =
#n!
#r!(n−r)!
#,where r ≤ n, n! = n×(n−1)×...×3×2×1, and 0! = 1.
#It is not until n = 23, that a value exceeds one-million: 23C10 = 1144066.
#How many, not necessarily distinct, values of nCr, for 1 ≤ n ≤ 100, are greater than one-million?
#Answer:
#4075
from time import time; t=time()
M = 1000000
s = 0
for n in range(23, 101):
c = n
for r in range(2, n//2+1):
c = c*(n+1-r)//r
if c > M:
s += n+1-2*r
break
print(s)#, time()-t