Google guide · Coding
Google coding interview questions
201 questions, tiered for the Google loop. Original problems (no LeetCode text) covering the patterns that recur in Google coding rounds: arrays, strings, trees, graphs, dynamic programming, and the data-structure design questions that show up as follow-ups.
Each interviewer rates you on four axes: coding, algorithms and data structures, communication, and problem solving. A round is meant to take you from a medium problem through one or two follow-ups. The bar is clean, working, bug-free code with correct complexity analysis, written in an editor with no autocomplete and no execution. Talking through your approach before coding is expected and scored.
Other Google lists: System design · Problem solving
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must86 questions
Solve these cold. They cover the patterns this loop leans on hardest.
- 3Sum
- Accounts Merge
- Alien Dictionary
- All Nodes Distance K in Binary Tree
- Basic Calculator
- Basic Calculator II
- Best Time to Buy and Sell Stock
- Binary Search Tree Iterator
- Binary Tree Level Order Traversal
- Binary Tree Maximum Path Sum
- Binary Tree Right Side View
- Binary Tree Vertical Order Traversal
- Clone Graph
- Coin Change
- Combination Sum
- Container With Most Water
- Copy List with Random Pointer
- Course Schedule
- Course Schedule II
- Daily Temperatures
- Decode String
- Decode Ways
- Design Hit Counter
- Diameter of Binary Tree
- Edit Distance
- Evaluate Division
- Find Median from Data Stream
- Find Peak Element
- Flatten Nested List Iterator
- Fruit Into Baskets
- Generate Parentheses
- Group Anagrams
- House Robber
- Implement Trie (Prefix Tree)
- Insert Delete GetRandom O(1)
- Insert Interval
- K Closest Points to Origin
- Koko Eating Bananas
- Kth Largest Element in an Array
- Largest Rectangle in Histogram
- Letter Combinations of a Phone Number
- Logger Rate Limiter
- Longest Common Subsequence
- Longest Consecutive Sequence
- Longest Increasing Subsequence
- Longest Palindromic Substring
- Longest Substring with At Most K Distinct Characters
- Longest Substring Without Repeating Characters
- Lowest Common Ancestor of a Binary Tree
- LRU Cache
- Maximum Subarray
- Median of Two Sorted Arrays
- Meeting Rooms II
- Merge Intervals
- Merge K Sorted Lists
- Merge Two Sorted Lists
- Min Stack
- Minimum Window Substring
- My Calendar I
- Network Delay Time
- Number of Islands
- Pacific Atlantic Water Flow
- Permutations
- Product of Array Except Self
- Random Pick with Weight
- Reverse Linked List
- Rotting Oranges
- Search in Rotated Sorted Array
- Serialize and Deserialize Binary Tree
- Shortest Path in Binary Matrix
- Sliding Window Maximum
- Spiral Matrix
- Split Array Largest Sum
- Subarray Sum Equals K
- Subsets
- Task Scheduler
- Time Based Key-Value Store
- Top K Frequent Elements
- Trapping Rain Water
- Two Sum
- Valid Parentheses
- Validate Binary Search Tree
- Word Break
- Word Ladder
- Word Search
- Word Search II
should92 questions
Work through once, then revisit any you could not finish on paper.
- Add Two Numbers
- Asteroid Collision
- Balanced Binary Tree
- Best Time to Buy and Sell Stock with Cooldown
- Binary Search
- Bus Routes
- Capacity To Ship Packages Within D Days
- Car Fleet
- Cheapest Flights Within K Stops
- Climbing Stairs
- Coin Change II
- Combination Sum II
- Construct Binary Tree from Preorder and Inorder Traversal
- Contains Duplicate
- Contiguous Array
- Continuous Subarray Sum
- Count Good Nodes in Binary Tree
- Design Add and Search Words Data Structure
- Employee Free Time
- Encode and Decode Strings
- Evaluate Reverse Polish Notation
- Find All Duplicates in an Array
- Find First and Last Position of Element in Sorted Array
- Find Minimum in Rotated Sorted Array
- First Missing Positive
- Flatten Binary Tree to Linked List
- Game of Life
- Gas Station
- Graph Valid Tree
- House Robber II
- Interleaving String
- Invert Binary Tree
- Is Graph Bipartite?
- Jump Game
- Jump Game II
- Kth Largest Element in a Stream
- Kth Smallest Element in a BST
- Kth Smallest Element in a Sorted Matrix
- LFU Cache
- Linked List Cycle
- Longest Repeating Character Replacement
- Longest Substring with At Most Two Distinct Characters
- Lowest Common Ancestor of a Binary Search Tree
- Majority Element
- Max Area of Island
- Max Consecutive Ones III
- Maximal Square
- Maximum Depth of Binary Tree
- Maximum Product Subarray
- Meeting Rooms
- Min Cost to Connect All Points
- Minimum Path Sum
- Minimum Size Subarray Sum
- Missing Ranges
- Move Zeroes
- N-Queens
- Non-overlapping Intervals
- Number of Connected Components in an Undirected Graph
- Paint House
- Palindrome Partitioning
- Palindromic Substrings
- Partition Equal Subset Sum
- Partition Labels
- Peeking Iterator
- Perfect Squares
- Permutation in String
- Pow(x, n)
- Range Sum Query - Immutable
- Reconstruct Itinerary
- Redundant Connection
- Regular Expression Matching
- Remove K Digits
- Remove Nth Node From End of List
- Reorder List
- Reorganize String
- Rotate Array
- Rotate Image
- Search a 2D Matrix
- Set Matrix Zeroes
- Single Number
- Sort Colors
- Squares of a Sorted Array
- String to Integer (atoi)
- Subsets II
- Subtree of Another Tree
- Surrounded Regions
- Swim in Rising Water
- Target Sum
- Unique Paths
- Valid Anagram
- Valid Palindrome
- Walls and Gates
stretch23 questions
Only if the must and should lists feel easy. Commonly reported at senior levels or as follow-ups.
- 3Sum Closest
- Burst Balloons
- Candy
- Count Number of Nice Subarrays
- Counting Bits
- Delete and Earn
- Distinct Subsequences
- Hand of Straights
- Longest Arithmetic Subsequence
- Maximum Sum Circular Subarray
- Merge Sorted Array
- Min Cost Climbing Stairs
- Minimum Height Trees
- Minimum Interval to Include Each Query
- Next Greater Element II
- Number of 1 Bits
- Number of Islands II
- Number of Longest Increasing Subsequence
- Remove Duplicates from Sorted Array
- Reverse Bits
- Same Tree
- Subarrays with K Different Integers
- Sum of Two Integers
13 must-tier questions with full solutions
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Questions people ask
Are these the real Google coding questions?
They are original questions built around the patterns commonly reported from Google loops, not leaked or copied problems. Interviewers rotate questions constantly; preparing by pattern and tier is what transfers.
What do must / should / stretch mean?
Must: the patterns a Google coding round leans on hardest; solve them cold. Should: work once and revisit. Stretch: senior-level or follow-up material.
What is free?
Every problem statement, examples and hints on this list. One coding question is fully open as a preview, and signing in unlocks the 13-question starter pack. The worked approach, solution, tests and per-company notes are in the guide.