Python Cheat Sheet - Interview Question

Question	Code	Question	Code
Check if list contains integer x	l = [3, 4, 5, 2, 11, 5] print(111 in l) # True	Get missing number in range [1...100]	def get_missing_number(lst): return set(range(1, len(lst)+1)) - set(lst) l = list(range(1,100)) l.remove(50) print(get_missing_number(l)) # 50
Find duplicate number in integer list	def find_duplicates(elements): duplicates, seen = set(), set() for element in elements: if element in seen: duplicates.add(element) seen.add(element) return duplicates	Compute the intersection of two lists	def intersect(lst1, lst2): res, lst2_copy = [], lst2[:] for el in lst1: if el in lst2_copy: res.append(el) lst2_copy.remove(el) return res
Check if two strings are anagrams	def is_anagram(s1, s2): return set(s1) == set(s2) print(is_anagram("elvis", "lives")) # True	Find max and min in unsorted list	l = [4, 3, 6, 3, 4, 888, 1, -11, 22, 3] print(max(l)) # 888 print(min(l)) # -11
Remove all duplicates from list	lst = list(range(10)) + list(range(10)) lst = list(set(lst)) print(lst) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]	Reverse string using recursion	def reverse(string): if len(string) < 1: return string return reverse(string[1:]) + string[0] print(reverse("hello")) # olleh
Find pairs of integers in list so that their sum is equal to integer x	def find_pairs(l, x): pairs = [] for (i, el1) in enumerate(l): for (j, el2) in enumerate(l[i+1:]): if el1 + el2 == x: pairs.append((el1, el2)) return pairs	Compute the first n Fibonacci numbers	a, b = 0, 1 n = 10 for i in range(n): print(b) a, b = b, a+b # 1, 1, 2, 3, 5, 8, ...
Check if a string is a palindrome	def is_palindrome(phrase): return phrase == phrase[::-1] print(is_palindrome("anna")) # True	Sort list with Quicksort algorithm	def qsort(L): if L == []: return L return qsort([x for x in L[1:] if x < L[0]]) + [L[0]] + qsort([x for x in L[1:] if x >=L[0]]) lst = [44, 33, 22, 55, 77, 999] print(qsort(lst)) # [22, 33, 44, 55, 77, 999]
Use list as stack, array, and queue	# as a list ... l = [3, 4] l += [5, 6] # [3, 4, 5, 6] # ... as a stack ... l.append(10) # [3, 4, 5, 6, 10] l.pop() # [3, 4, 5, 6] # ... and as a queue l.insert(0, 5) # [5, 3, 4, 5, 6] l.pop(0) # [3, 4, 5, 6]	Find all permutation of string	def get_permutations(w): if len(w)<=1: return set(w) smaller = get_permutations(w[1:]) perms = set() for x in smaller: for pos in range(0,len(x)+1): perm = x[:pos] + w[0] + x[pos:] perms.add(perm) return perms print(get_permutations("nan")) # {'nna', 'ann', 'nan'}

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