https://projecteuler.net/problem=7

10001st prime

Problem 7

Published
on Friday, 28th December 2001, 06:00 pm; Solved by 257306; Difficulty rating: 5%

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10 001st prime number?

 

本来想用最笨的方法，从小到大一个一个算，后来看到素筛法，就随便写了些，还是感觉，如果数量再大，这个方法也不好用

upper = 200010
listprime = [True] * (upper+1)
for i in range(2,upper+1):
if listprime[i] == True:
temp = i * 2
while temp < upper:
listprime[temp] = False
temp += i
count = 0
i = 2
while count < 10001 and i < upper:
if listprime[i] == True:
count += 1
i += 1

print(i-1)
print(count)