Rare numbers: Difference between revisions
→{{header|Python}}
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===naively optimized===
A mess of code that can return the first 5 rare numbers in 5m5s on a i7-7700k.
<syntaxhighlight lang="python">
# rare.py
# by xing216
import time as t
from functools import cache
@cache
def isSquare(n: int) ->bool:
if n < 0:
return False
if n == 0:
return True
while n&3 == 0:
n=n>>2
if n&7 != 1:
return False
if n==1:
return True
c = n%10
if c in {3, 7}:
return False
if n % 7 in {3, 5, 6}:
return False
if n % 9 in {2,3,5,6,8}:
return False
if n % 13 in {2,5,6,7,8,11}:
return False
if c == 5:
if (n//10)%10 != 2:
return False
if (n//100)%10 not in {0,2,6}:
return False
if (n//100)%10 == 6:
if (n//1000)%10 not in {0,5}:
return False
else:
if (n//10)%4 != 0:
return False
s = (len(str(n))-1) // 2
x = (10**s) * 4
A = {x, n}
while x * x != n:
x = (x + (n // x)) >> 1
if x in A:
return False
A.add(x)
return True
@cache
def main() -> None:
r = 1
start = t.time()
while True:
strr = str(r)
if int(strr[0]) % 2 != 0:
r += int('1' + (len(strr)-1)*'0' )
r1 = int(strr[::-1])
x = r + r1
y = r - r1
if isSquare(x) and isSquare(y) and r != r1:
print(f'success: {r} ~{t.time()-start}s')
r+=1
if __name__ == '__main__':
main()
</syntaxhighlight>
=={{header|Quackery}}==
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