Second Maximum of list of integers without comparison, loop or recursion

Δεκέμβριος 5, 2016Σεπτέμβριος 20, 2018 ~ Δημήτρης Καλοψικάκης

Function sm() returns a tuple of the maximum and second maximum of a list of integers without any comparison or loop.

#!/usr/bin/python3

from functools import *

# Returns 1 if a>b, else 0.
gt = lambda a,b: ( (b-a)>>((b-a).bit_length()) ) & 0x1
gtn = lambda a,b: (b == None) or gt(a,b)

# a<=b. Returns 1 if a<y<b, else 0.
btn = lambda a,b,y: gtn(y,a) and gtn(b,y)

# (neq) Returns 0 if a=b, 1 otherwise --not needed.
neq = lambda a,b: gt(a,b)+gt(b,a)
eq = lambda a,b: not neq(a,b)

# t=(a,b). Returns (x2,x1) where
# x1 is max of a,b,y and x2 is second max of a,b,y.
m2 = lambda t,y: (t[1],y) if gtn(y,t[1]) \
else ( (y,t[1]) if btn(t[0],t[1],y) \
else (t[0],t[1]))
# Executes m2() cumulatively on l.
sm = lambda l: reduce(m2,l, (None,None))[0]

Create Random password with Python

Σεπτέμβριος 25, 2016Σεπτέμβριος 20, 2018 ~ Δημήτρης Καλοψικάκης

This piece of code creates a password of 10 characters, with letters, digits and punctuation.

#!/usr/bin/python3

import string
import random

print(''.join(random.choice(string.ascii_letters + \
                            string.digits + \
                            string.punctuation) \
                            for x in range(10) \
             ) \ 
     )

Swap without tmp

Σεπτέμβριος 22, 2016Σεπτέμβριος 20, 2018 ~ Δημήτρης Καλοψικάκης

1st way:

a = a + b
b = a - b
a = a - b

2nd way:

a = a ^ b
b = a ^ b
a = a ^ b