Language-Specific Prep
Python Coding Interview Questions (2026)
Python is the most popular language for coding interviews. Its concise syntax, built-in data structures, and readable style let you write correct solutions 30–50% faster than Java or C++. Interviewers at Google, Meta, and Amazon all accept Python — and many prefer it because it keeps the focus on algorithmic thinking rather than syntax.
321 problems with Python solutions
45 Easy 256 Medium 20 Hard
Why Python for Coding Interviews
Strengths
- ✓ Concise syntax — 30-50% less code than Java/C++ for the same algorithm
- ✓ Built-in data structures: list, dict, set, deque, heapq, Counter, defaultdict
- ✓ List comprehensions and generator expressions for clean one-liners
- ✓ No type declarations needed — write faster under time pressure
- ✓ sorted() with key= eliminates custom comparator boilerplate
- ✓ Dynamically typed — no generics or autoboxing overhead
Watch Out For
- ⚠ No built-in priority queue class (use heapq module)
- ⚠ Slower runtime — but runtime speed almost never matters in interviews
- ⚠ No static typing — some companies prefer typed languages
- ⚠ Recursion limit (default 1000) — need sys.setrecursionlimit for deep DFS
Must-Know Python Features for Interviews
heapq for priority queues — heapq.heappush, heapq.heappop, heapify)
collections.Counter for frequency maps
collections.defaultdict for auto-initializing maps
collections.deque for O — 1) append/pop from both ends
bisect for binary search on sorted lists
itertools for permutations, combinations, and chain
functools.lru_cache for memoization — DP problems)
String slicing: s[i:j], s[::-1] for reversal
dict.get — key, default) to avoid KeyError
zip, enumerate, any, all for clean iteration
Python Interview Tips
Use collections.Counter instead of manual frequency maps
Instead of building a frequency dict with a loop, use Counter(s) for strings or Counter(arr) for arrays. It is O(n) and cleaner than the manual approach. Example: Counter("hello") returns Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1}).
Use heapq for all heap/priority queue problems
Python has no built-in PriorityQueue class you need — just use the heapq module. heapq.heappush(heap, val) and heapq.heappop(heap) give O(log n) operations. For a max-heap, negate values: heapq.heappush(heap, -val). For kth largest, maintain a heap of size k.
Memoize DP with @lru_cache
For recursive DP problems, add @lru_cache(maxsize=None) above your function. This auto-memoizes all calls. For top-down DP in interviews, this is 2 lines of code vs. writing a manual memo dict. Example: @lru_cache(maxsize=None) def dp(i): ...
Use defaultdict to avoid KeyError
defaultdict(list) auto-creates empty lists for missing keys. defaultdict(int) auto-creates 0. defaultdict(lambda: float("inf")) for infinity defaults. This eliminates the "if key not in dict" pattern entirely.
List comprehensions for one-pass transforms
Use [x*2 for x in arr] instead of a loop with append. Nested: [x for row in matrix for x in row]. Conditional: [x for x in arr if x > 0]. These are faster than loops and read better under interview pressure.
String reverse: s[::-1]
Python slicing makes reversal trivial: s[::-1] reverses a string, s[i:j+1][::-1] reverses a substring. No need to convert to list and back. For palindromes, check s == s[::-1].
Python Coding Interview Problems by Pattern
⊞
Sliding Window
(27) ⇄
Two Pointers
(51) ⌖
Binary Search
(34) Σ
Prefix Sum
(9)| Subarray Sum Equals K | Medium | Python → |
| Product of Array Except Self | Medium | Python → |
| Range Sum Query - Immutable | Easy | Python → |
| Contiguous Array | Medium | Python → |
| Find Pivot Index | Easy | Python → |
| Running Sum of 1D Array | Easy | Python → |
| Minimum Average Difference | Medium | Python → |
| Max Chunks To Make Sorted | Medium | Python → |
| Max Chunks To Make Sorted II | Medium | Python → |
#
Hash Map / Set
(12)| Two Sum | Easy | Python → |
| Group Anagrams | Medium | Python → |
| Top K Frequent Elements | Medium | Python → |
| Valid Anagram | Easy | Python → |
| Longest Consecutive Sequence | Medium | Python → |
| Contains Duplicate | Easy | Python → |
| Word Pattern | Easy | Python → |
| Isomorphic Strings | Easy | Python → |
| LRU Cache | Medium | Python → |
| 4Sum II | Medium | Python → |
| Number of Good Pairs | Easy | Python → |
| Subarray Sum Divisible by K | Medium | Python → |
⬚
Stack
(22)| Valid Parentheses | Easy | Python → |
| Min Stack | Medium | Python → |
| Evaluate Reverse Polish Notation | Medium | Python → |
| Daily Temperatures | Medium | Python → |
| Decode String | Medium | Python → |
| Asteroid Collision | Medium | Python → |
| Remove K Digits | Medium | Python → |
| Car Fleet | Medium | Python → |
| Basic Calculator II | Medium | Python → |
| Simplify Path | Medium | Python → |
| Next Largest Element to Right | Medium | Python → |
| Next Largest Element to Left | Medium | Python → |
| Next Smallest Element to Left | Medium | Python → |
| Next Smallest Element to Right | Medium | Python → |
| Maximum Area Rectangle in Binary Matrix | Medium | Python → |
| Minimum Element in Stack with Extra Space | Medium | Python → |
| Minimum Element in Stack in O | Medium | Python → |
| Implement Queue using Stack | Medium | Python → |
| Implement Stack using Queues | Medium | Python → |
| Remove All Occurrences of a Substring | Medium | Python → |
| Minimum invalid parentheses to remove to make valid parentheses | Easy | Python → |
| Minimum Add to Make Parentheses Valid | Medium | Python → |
▷
Queue / BFS
(10)| Number of Islands | Medium | Python → |
| Rotting Oranges | Medium | Python → |
| Binary Tree Level Order Traversal | Medium | Python → |
| Word Ladder | Hard | Python → |
| 01 Matrix | Medium | Python → |
| Walls and Gates | Medium | Python → |
| Shortest Path in Binary Matrix | Medium | Python → |
| Open the Lock | Medium | Python → |
| Minimum Genetic Mutation | Medium | Python → |
| Jump Game III | Medium | Python → |
△
Heap / Priority Queue
(14) ⟶
Linked List
(24)| Reverse Linked List | Easy | Python → |
| Linked List Cycle | Easy | Python → |
| Merge Two Sorted Lists | Easy | Python → |
| Reorder List | Medium | Python → |
| Add Two Numbers | Medium | Python → |
| Remove Nth Node From End of List | Medium | Python → |
| Copy List with Random Pointer | Medium | Python → |
| Palindrome Linked List | Easy | Python → |
| Swap Nodes in Pairs | Medium | Python → |
| Rotate List | Medium | Python → |
| Reverse Nodes in k-Group | Hard | Python → |
| Find the intersection of two linked lists | Medium | Python → |
| Middle of the Linked List | Easy | Python → |
| Add Two Numbers Represented in Linked List | Medium | Python → |
| Linked List Cycle II | Medium | Python → |
| Remove Duplicates from Sorted List | Easy | Python → |
| Remove Duplicates from Sorted List - II | Easy | Python → |
| Add Two Numbers II | Medium | Python → |
| Odd Even Linked List | Medium | Python → |
| Reverse a Linked List in groups of given size k | Medium | Python → |
| Reverse Linked List II | Medium | Python → |
| Convert Binary Number in a Linked List to Integer | Medium | Python → |
| Partition List | Medium | Python → |
| Sort List | Medium | Python → |
🌲
Trees / DFS
(18) ◉
Graphs
(10)| Clone Graph | Medium | Python → |
| Pacific Atlantic Water Flow | Medium | Python → |
| Number of Connected Components in Undirected Graph | Medium | Python → |
| Surrounded Regions | Medium | Python → |
| Minimum Height Trees | Medium | Python → |
| Network Delay Time | Medium | Python → |
| Find Eventual Safe States | Medium | Python → |
| All Paths From Source to Target | Medium | Python → |
| Cheapest Flights Within K Stops | Medium | Python → |
| Graph Valid Tree | Medium | Python → |
◫
Dynamic Programming
(26)| Climbing Stairs | Easy | Python → |
| House Robber | Medium | Python → |
| Coin Change | Medium | Python → |
| Longest Increasing Subsequence | Medium | Python → |
| Longest Common Subsequence | Medium | Python → |
| Word Break | Medium | Python → |
| Edit Distance | Hard | Python → |
| Unique Paths | Medium | Python → |
| Maximum Subarray | Medium | Python → |
| Decode Ways | Medium | Python → |
| Min Cost Climbing Stairs | Easy | Python → |
| House Robber II | Medium | Python → |
| Partition Equal Subset Sum | Medium | Python → |
| Target Sum | Medium | Python → |
| Best Time to Buy and Sell Stock | Easy | Python → |
| Palindromic Substrings | Medium | Python → |
| Longest Palindromic Substring | Medium | Python → |
| Best Time to Buy and Sell Stock with Cooldown | Medium | Python → |
| Maximum Product Subarray | Medium | Python → |
| Triangle | Medium | Python → |
| Minimum Path Sum | Medium | Python → |
| Perfect Squares | Medium | Python → |
| Regular Expression Matching | Hard | Python → |
| Interleaving String | Medium | Python → |
| Best Time to Buy and Sell Stock with Transaction Fee | Medium | Python → |
| Integer Break | Medium | Python → |
◈
Greedy
(8)| Jump Game | Medium | Python → |
| Jump Game II | Medium | Python → |
| Gas Station | Medium | Python → |
| Non-overlapping Intervals | Medium | Python → |
| Meeting Rooms II | Medium | Python → |
| Queue Reconstruction by Height | Medium | Python → |
| Minimum Number of Arrows to Burst Balloons | Medium | Python → |
| Candy | Hard | Python → |
↩
Backtracking
(14)| Permutations | Medium | Python → |
| Subsets | Medium | Python → |
| Combination Sum | Medium | Python → |
| Word Search | Medium | Python → |
| Letter Combinations of a Phone Number | Medium | Python → |
| Generate Parentheses | Medium | Python → |
| N-Queens | Hard | Python → |
| Palindrome Partitioning | Medium | Python → |
| Combination Sum II | Medium | Python → |
| Subsets II | Medium | Python → |
| Next Permutation | Medium | Python → |
| Find all permutations of a string | Medium | Python → |
| Find all permutations of a given string without duplicates | Medium | Python → |
| Longest Valid Parentheses | Easy | Python → |
T
Trie
(5)| Implement Trie (Prefix Tree) | Medium | Python → |
| Design Add and Search Words Data Structure | Medium | Python → |
| Word Search II | Hard | Python → |
| Longest Word in Dictionary | Medium | Python → |
| Replace Words | Medium | Python → |
∪
Union Find
(6)| Redundant Connection | Medium | Python → |
| Accounts Merge | Medium | Python → |
| Number of Provinces | Medium | Python → |
| Satisfiability of Equality Equations | Medium | Python → |
| Swim in Rising Water | Hard | Python → |
| Most Stones Removed with Same Row or Column | Medium | Python → |
↗
Monotonic Stack
(7)| Largest Rectangle in Histogram | Hard | Python → |
| Next Greater Element I | Easy | Python → |
| Sum of Subarray Minimums | Medium | Python → |
| Online Stock Span | Medium | Python → |
| 132 Pattern | Medium | Python → |
| Remove Duplicate Letters | Medium | Python → |
| Stock Span Problem | Medium | Python → |
→
Topological Sort
(5)| Course Schedule | Medium | Python → |
| Course Schedule II | Medium | Python → |
| Parallel Courses | Medium | Python → |
| Sequence Reconstruction | Medium | Python → |
| Alien Dictionary | Hard | Python → |
&
Bit Manipulation
(8)| Single Number | Easy | Python → |
| Missing Number | Easy | Python → |
| Counting Bits | Easy | Python → |
| Number of 1 Bits | Easy | Python → |
| Reverse Bits | Easy | Python → |
| Sum of Two Integers | Medium | Python → |
| Single Number II | Medium | Python → |
| Power of Two | Easy | Python → |
⊣⊢
Intervals
(4)| Merge Intervals | Medium | Python → |
| Insert Interval | Medium | Python → |
| Minimum Interval to Include Each Query | Hard | Python → |
| Meeting Rooms | Easy | Python → |
⊠
Matrix
(7)| Rotate Image | Medium | Python → |
| Spiral Matrix | Medium | Python → |
| Set Matrix Zeroes | Medium | Python → |
| Maximal Square | Medium | Python → |
| Game of Life | Medium | Python → |
| Search a 2D Matrix II | Medium | Python → |
| Count Negative Numbers in a Sorted Matrix | Easy | Python → |
Frequently Asked Questions
Is Python accepted in coding interviews at FAANG companies?
Yes — Google, Meta, Amazon, Apple, and Microsoft all accept Python for coding interviews. Python is actually the most popular interview language at these companies because its concise syntax lets you focus on algorithmic thinking rather than boilerplate. The interviewer cares about your approach, not your language.
What Python features are most useful for coding interviews?
The most useful Python features for interviews are: collections.Counter for frequency maps, collections.defaultdict for auto-initializing dicts, heapq for priority queues, bisect for binary search, @lru_cache for memoization, and list comprehensions for clean transforms. These eliminate boilerplate and let you write correct solutions faster.
Should I use Python or C++ for coding interviews?
Use Python unless you are specifically interviewing for competitive programming, game development, or HFT roles that require C++. Python lets you write 30-50% less code with the same algorithmic complexity. Interviewers care about your problem-solving approach, not runtime performance. Python's built-in data structures (Counter, defaultdict, heapq) are sufficient for 99% of interview problems.
How do I handle recursion limits in Python during interviews?
Python's default recursion limit is 1000. For deep DFS on trees/graphs with more than 1000 nodes, add "import sys; sys.setrecursionlimit(10000)" at the top of your solution. In a real interview, mention this to the interviewer — it shows you know the language well. Alternatively, convert recursive DFS to iterative using an explicit stack.
What are the most common Python mistakes in coding interviews?
Common Python mistakes: 1) Forgetting that strings are immutable (s[i] = "x" raises TypeError — use s[:i] + "x" + s[i+1:]). 2) Modifying a list while iterating over it. 3) Using "is" instead of "==" for value comparison. 4) Not handling the empty input edge case. 5) Using a mutable default argument like def f(arr=[]).
Ready to start practicing?
Browse all problems with Python solutions, or follow the pattern-based roadmap.