DEV Community: ETHAN LEONG _

Recursion

ETHAN LEONG _ — Fri, 28 Mar 2025 07:50:39 +0000

check palindrome:

def is_palindrome(s):
if len(s) <= 1:
return True
if s[0] != s[-1]:
return False
return is_palindrome(s[1:-1])

permutations of string

def permute(s, answer=''):
if len(s) == 0:
print(answer)
return
for i in range(len(s)):
ch = s[i]
left = s[:i]
right = s[i+1:]
permute(left + right, answer + ch)

subsets

def subsets(s, current=""):
if len(s) == 0:
print(current)
return
subsets(s[1:], current) # Exclude
subsets(s[1:], current + s[0]) # Include

tower of hanoi

def hanoi(n, source, target, auxiliary):
if n == 0:
return
hanoi(n - 1, source, auxiliary, target)
print(f"Move disk {n} from {source} to {target}")
hanoi(n - 1, auxiliary, target, source)

nth stair

def count_ways(n):
if n <= 1:
return 1
return count_ways(n - 1) + count_ways(n - 2)

Prime Function

ETHAN LEONG _ — Fri, 28 Mar 2025 07:34:25 +0000

def get_primes(n):
primes = []
candidate = 2
while len(primes) < n:
for p in primes:
if candidate % p == 0:
break
else:
primes.append(candidate)
candidate += 1
return primes

Recursion Power Sum

ETHAN LEONG _ — Thu, 27 Mar 2025 15:59:40 +0000

def powerSum(X, N, num=1):
power = num ** N

if power > X:
    return 0  # too big, can't continue
elif power == X:
    return 1  # exact match found
else:
    # either include this number or skip it
    return powerSum(X - power, N, num + 1) + powerSum(X, N, num + 1)

Sort Dictionary

ETHAN LEONG _ — Thu, 27 Mar 2025 13:34:42 +0000

student_scores = {
'Alex': 88,
'Ben': 75,
'Cyrus': 93,
'Denver': 85
}
sorted_by_values = dict(sorted(student_scores.items(), key=lambda item: item[1]))
print(sorted_by_values)

{'Ben': 75, 'Denver': 85, 'Alex': 88, 'Cyrus': 93}