### Grokking the Coding Interview: Patterns for Coding Questions

Fast track your coding interview prep by learning coding patterns. Act smartly, and follow the coding patterns.
Level:
Intermediate
Study Time:
336h
Lessons:
495
Playgrounds :
534
211,991 (Students)
Course Overview

Coding interviews are getting harder every day. A few years back, brushing up on key data structures and going through 50-75 coding interview questions was more than enough prep for an interview. Today, everyone has access to massive sets of coding problems, and they have gotten more difficult to account for that. The process has gotten more competitive.

When our team sat together to brainstorm on ideas to make the interview process easier for candidates, we realized quickly that one skill helped us the most when we were preparing for coding interviews: "the ability to map a new problem to an already known problem."

To help candidates with that, we have come up with a list of 27 common coding patterns to help solve coding questions. The idea is, once you are familiar with a pattern, you'll be able to solve dozens of problems with it.

The techniques taught in this course have helped developers land jobs in top companies including Google, Facebook, Amazon, and Microsoft.

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Course Content
36 Chapters • 495 Lessons
1.
Introduction
2 lessons
Who Should Take This Course?
Course Overview
2.
Warmup
17 lessons
Why warmup?
Contains Duplicate (easy)
Solution: Contains Duplicate
Pangram (easy)
Solution: Pangram
Reverse Vowels (easy)
Solution: Reverse Vowels
Valid Palindrome (easy)
Solution: Valid Palindrome
Valid Anagram (easy)
Solution: Valid Anagram
Shortest Word Distance (easy)
Solution: Shortest Word Distance
Number of Good Pairs (easy)
Solution: Number of Good Pairs
Sqrt (medium)
Solution: Sqrt
Introduction to Two Pointers Pattern
Pair with Target Sum (easy)
Solution: Pair with Target Sum
Find Non-Duplicate Number Instances (easy)
Solution: Find Non-Duplicate Number Instances
Squaring a Sorted Array (easy)
Solution: Squaring a Sorted Array
Triplet Sum to Zero (medium)
Solution: Triplet Sum to Zero
Triplet Sum Close to Target (medium)
Solution: Triplet Sum Close to Target
Triplets with Smaller Sum (medium)
Solution: Triplets with Smaller Sum
Subarrays with Product Less than a Target (medium)
Solution: Subarrays with Product Less than a Target
Dutch National Flag Problem (medium)
Solution: Dutch National Flag Problem
Problem Challenge 1: Quadruple Sum to Target (medium)
Solution: Problem Challenge 1: Quadruple Sum to Target
Problem Challenge 2: Comparing Strings containing Backspaces (medium)
Solution: Problem Challenge 2: Comparing Strings containing Backspaces
Problem Challenge 3: Minimum Window Sort (medium)
Solution: Problem Challenge 3: Minimum Window Sort
Introduction to Fast & Slow Pointers Pattern
Happy Number (medium)
Solution: Happy Number
Problem Challenge 1: Palindrome LinkedList (medium)
Solution: Problem Challenge 1: Palindrome LinkedList
Problem Challenge 2: Rearrange a LinkedList (medium)
Solution: Problem Challenge 2: Rearrange a LinkedList
Problem Challenge 3: Cycle in a Circular Array (hard)
Solution: Problem Challenge 3: Cycle in a Circular Array
Introduction to Sliding Window Pattern
Maximum Sum Subarray of Size K (easy)
Solution: Maximum Sum Subarray of Size K
Smallest Subarray With a Greater Sum (easy)
Solution: Smallest Subarray With a Greater Sum
Longest Substring with K Distinct Characters (medium)
Solution: Longest Substring with K Distinct Characters
Longest Substring with Same Letters after Replacement (hard)
Solution: Longest Substring with Same Letters after Replacement
Longest Subarray with Ones after Replacement (hard)
Solution: Longest Subarray with Ones after Replacement
Problem Challenge 1: Permutation in a String (hard)
Solution: Problem Challenge 1: Permutation in a String
Problem Challenge 2: String Anagrams (hard)
Solution: Problem Challenge 2: String Anagrams
Problem Challenge 3: Smallest Window containing Substring (hard)
Solution: Problem Challenge 3: Smallest Window containing Substring
Problem Challenge 4: Words Concatenation (hard)
Solution: Problem Challenge 4: Words Concatenation
Introduction to Merge Intervals Pattern
Merge Intervals (medium)
Solution: Merge Intervals
Insert Interval (medium)
Solution: Insert Interval
Intervals Intersection (medium)
Solution: Intervals Intersection
Conflicting Appointments (medium)
Solution: Conflicting Appointments
Problem Challenge 1: Minimum Meeting Rooms (hard)
Solution: Problem Challenge 1: Minimum Meeting Rooms
Problem Challenge 2: Maximum CPU Load (hard)
Solution: Problem Challenge 2: Maximum CPU Load
Problem Challenge 3: Employee Free Time (hard)
Solution: Problem Challenge 3: Employee Free Time
Introduction to Cyclic Sort Pattern
Cyclic Sort (easy)
Solution: Cyclic Sort
Find the Missing Number (easy)
Solution: Find the Missing Number
Find all Missing Numbers (easy)
Solution: Find all Missing Numbers
Find the Duplicate Number (easy)
Solution: Find the Duplicate Number
Find all Duplicate Numbers (easy)
Solution: Find all Duplicate Numbers
Problem Challenge 1: Find the Corrupt Pair (easy)
Solution: Problem Challenge 1: Find the Corrupt Pair
Problem Challenge 2: Find the Smallest Missing Positive Number (medium)
Solution: Problem Challenge 2: Find the Smallest Missing Positive Number
Problem Challenge 3: Find the First K Missing Positive Numbers (hard)
Solution: Problem Challenge 3: Find the First K Missing Positive Numbers
Introduction to In-place Reversal of a Linked List Pattern
Reverse a Sub-list (medium)
Solution: Reverse a Sub-list
Reverse every K-element Sub-list (medium)
Solution: Reverse every K-element Sub-list
Problem Challenge 1: Reverse alternating K-element Sub-list (medium)
Solution: Problem Challenge 1: Reverse alternating K-element Sub-list
Problem Challenge 2: Rotate a LinkedList (medium)
Solution: Problem Challenge 2: Rotate a LinkedList
Introduction to Stack
Operations on Stack
Implementing Stack Data Structure
Applications of Stack
Problem 1: Balanced Parentheses
Solution: Balanced Parentheses
Problem 2: Reverse a String
Solution: Reverse a String
Problem 3: Decimal to Binary Conversion
Solution: Decimal to Binary Conversion
Problem 4: Next Greater Element
Solution: Next Greater Element
Problem 5: Sorting a Stack
Solution: Sorting a Stack
Problem 6: Simplify Path
Solution: Simplify Path
Introduction to Monotonic Stack
Remove Nodes From Linked List (easy)
Solution: Remove Nodes From Linked List
Remove All Adjacent Duplicates In String (easy)
Solution: Remove All Adjacent Duplicates In String
Next Greater Element (easy)
Solution: Next Greater Element
Daily Temperatures (easy)
Solution: Daily Temperatures
Remove All Adjacent Duplicates in String II (medium)
Solution: Remove All Adjacent Duplicates in String II
Remove K Digits (hard)
Solution: Remove K Digits
Introduction to Hashing
Introduction to Hash Tables
Issues with Hash Tables
Problem 1: First Non-repeating Character (easy)
Solution: First Non-repeating Character (easy)
Problem 2: Largest Unique Number (easy)
Solution: Largest Unique Number (easy)
Problem 3: Maximum Number of Balloons (easy)
Solution: Maximum Number of Balloons (easy)
Problem 4: Longest Palindrome(easy)
Solution: Longest Palindrome(easy)
Problem 5: Ransom Note (easy)
Solution: Ransom Note (easy)
Introduction to Tree Breadth First Search Pattern
Binary Tree Level Order Traversal (easy)
Solution: Binary Tree Level Order Traversal
Reverse Level Order Traversal (easy)
Solution: Reverse Level Order Traversal
Zigzag Traversal (medium)
Solution: Zigzag Traversal
Level Averages in a Binary Tree (easy)
Solution: Level Averages in a Binary Tree
Minimum Depth of a Binary Tree (easy)
Solution: Minimum Depth of a Binary Tree
Level Order Successor (easy)
Solution: Level Order Successor
Connect Level Order Siblings (medium)
Solution: Connect Level Order Siblings
Problem Challenge 1: Connect All Level Order Siblings (medium)
Solution: Problem Challenge 1: Connect All Level Order Siblings
Problem Challenge 2: Right View of a Binary Tree (easy)
Solution: Problem Challenge 2: Right View of a Binary Tree
Introduction to Tree Depth First Search Pattern
Binary Tree Path Sum (easy)
Solution: Binary Tree Path Sum
All Paths for a Sum (medium)
Solution: All Paths for a Sum
Sum of Path Numbers (medium)
Solution: Sum of Path Numbers
Path With Given Sequence (medium)
Solution: Path With Given Sequence
Count Paths for a Sum (medium)
Solution: Count Paths for a Sum
Problem Challenge 1: Tree Diameter (medium)
Solution: Problem Challenge 1: Tree Diameter
Problem Challenge 2: Path with Maximum Sum (hard)
Solution: Problem Challenge 2: Path with Maximum Sum
Introduction to Graph
Graph Representations
Graph as an Abstract Data Type (ADT)
Graph Traversal - Depth First Search(DFS)
Graph Traversal - Breadth First Search (BFS)
Problem 1: Find if Path Exists in Graph(easy)
Solution: Find if Path Exists in Graph(easy)
Problem 2: Number of Provinces (medium)
Solution: Number of Provinces (medium)
Problem 3: Minimum Number of Vertices to Reach All Nodes(medium)
Solution: Minimum Number of Vertices to Reach All Nodes(medium)
Introduction to Island Pattern
Number of Islands (easy)
Solution: Number of Islands
Biggest Island (easy)
Solution: Biggest Island
Flood Fill (easy)
Solution: Flood Fill
Number of Closed Islands (easy)
Solution: Number of Closed Islands
Problem Challenge 1 (easy)
Solution: Problem Challenge 1
Problem Challenge 2 (medium)
Solution: Problem Challenge 2
Problem Challenge 3 (medium)
Solution: Problem Challenge 3
Introduction to Two Heaps Pattern
Find the Median of a Number Stream (medium)
Solution: Find the Median of a Number Stream
Sliding Window Median (hard)
Solution: Sliding Window Median
Maximize Capital (hard)
Solution: Maximize Capital
Problem Challenge 1: Next Interval (hard)
Solution: Problem Challenge 1: Next Interval
Introduction to Subsets Pattern
Subsets (easy)
Solution: Subsets
Subsets With Duplicates (easy)
Solution: Subsets With Duplicates
Permutations (medium)
Solution: Permutations
String Permutations by changing case (medium)
Solution: String Permutations by changing case
Balanced Parentheses (hard)
Solution: Balanced Parentheses
Unique Generalized Abbreviations (hard)
Solution: Unique Generalized Abbreviations
Problem Challenge 1: Evaluate Expression (hard)
Solution: Problem Challenge 1: Evaluate Expression
Problem Challenge 2: Structurally Unique Binary Search Trees (hard)
Solution: Problem Challenge 2: Structurally Unique Binary Search Trees
Problem Challenge 3: Count of Structurally Unique Binary Search Trees (hard)
Solution: Problem Challenge 3: Count of Structurally Unique Binary Search Trees
Introduction to Modified Binary Search Pattern
Order-agnostic Binary Search (easy)
Solution: Order-agnostic Binary Search
Ceiling of a Number (medium)
Solution: Ceiling of a Number
Next Letter (medium)
Solution: Next Letter
Number Range (medium)
Solution: Number Range
Search in a Sorted Infinite Array (medium)
Solution: Search in a Sorted Infinite Array
Minimum Difference Element (medium)
Solution: Minimum Difference Element
Bitonic Array Maximum (easy)
Solution: Bitonic Array Maximum
Problem Challenge 1: Search Bitonic Array (medium)
Solution: Problem Challenge 1: Search Bitonic Array
Problem Challenge 2: Search in Rotated Array (medium)
Solution: Problem Challenge 2: Search in Rotated Array
Problem Challenge 3: Rotation Count (medium)
Solution: Problem Challenge 3: Rotation Count
Introduction to Bitwise XOR Pattern
Single Number (easy)
Solution: Single Number
Two Single Numbers (medium)
Solution: Two Single Numbers
Complement of Base 10 Number (medium)
Solution: Complement of Base 10 Number
Problem Challenge 1: Flip and Invert an Image (hard)
Solution: Problem Challenge 1: Flip and Invert an Image
Introduction to Top 'K' Elements Pattern
Top 'K' Numbers (easy)
Solution: Top 'K' Numbers
Kth Smallest Number (easy)
Solution: Kth Smallest Number
'K' Closest Points to the Origin (easy)
Solution: 'K' Closest Points to the Origin
Connect Ropes (easy)
Solution: Connect Ropes
Top 'K' Frequent Numbers (medium)
Solution: Top 'K' Frequent Numbers
Frequency Sort (medium)
Solution: Frequency Sort
Kth Largest Number in a Stream (medium)
Solution: Kth Largest Number in a Stream
'K' Closest Numbers (medium)
Solution: 'K' Closest Numbers
Maximum Distinct Elements (medium)
Solution: Maximum Distinct Elements
Sum of Elements (medium)
Solution: Sum of Elements
Rearrange String (hard)
Solution: Rearrange String
Problem Challenge 1: Rearrange String K Distance Apart (hard)
Solution: Problem Challenge 1: Rearrange String K Distance Apart
Problem Challenge 2: Scheduling Tasks (hard)
Solution: Problem Challenge 2: Scheduling Tasks
Problem Challenge 3: Frequency Stack (hard)
Solution: Problem Challenge 3: Frequency Stack
Introduction to K-way Merge Pattern
Merge K Sorted Lists (medium)
Solution: Merge K Sorted Lists
Kth Smallest Number in M Sorted Lists (medium)
Solution: Kth Smallest Number in M Sorted Lists
Kth Smallest Number in a Sorted Matrix (hard)
Solution: Kth Smallest Number in a Sorted Matrix
Smallest Number Range (hard)
Solution: Smallest Number Range
Problem Challenge 1: K Pairs with Largest Sums (hard)
Solution: Problem Challenge 1: K Pairs with Largest Sum
Introduction to Greedy Algorithm
Valid Palindrome II (easy)
Solution: Valid Palindrome II
Maximum Length of Pair Chain (medium)
Solution: Maximum Length of Pair Chain
Minimum Add to Make Parentheses Valid (medium)
Solution: Minimum Add to Make Parentheses Valid
Remove Duplicate Letters (medium)
Solution: Remove Duplicate Letters
Largest Palindromic Number (medium)
Solution: Largest Palindromic Number
Removing Minimum and Maximum From Array (medium)
Solution: Removing Minimum and Maximum From Array
Introduction to 0/1 Knapsack Pattern
0/1 Knapsack (medium)
Solution: 0/1 Knapsack
Equal Subset Sum Partition (medium)
Solution: Equal Subset Sum Partition
Subset Sum (medium)
Solution: Subset Sum
Minimum Subset Sum Difference (hard)
Solution: Minimum Subset Sum Difference
Problem Challenge 1: Count of Subset Sum (hard)
Solution: Problem Challenge 1: Count of Subset Sum
Problem Challenge 2: Target Sum (hard)
Solution: Problem Challenge 2: Target Sum
Introduction to Backtracking Pattern
Combination Sum (medium)
Solution: Combination Sum
Word Search (medium)
Solution: Word Search
Sudoku Solver (hard)
Solution: Sudoku Solver
Factor Combinations (medium)
Solution: Factor Combinations
Split a String Into the Max Number of Unique Substrings (medium)
Solution: Split a String Into the Max Number of Unique Substrings
Introduction to Trie
Implement Trie (Prefix Tree) (medium)
Solution: Implement Trie (Prefix Tree)
Index Pairs of a String (easy)
Solution: Index Pairs of a String
Design Add and Search Words Data Structure (medium)
Solution: Design Add and Search Words Data Structure
Extra Characters in a String (medium)
Solution: Extra Characters in a String
Search Suggestions System (medium)
Solution: Search Suggestions System
Introduction to Topological Sort Pattern
Topological Sort (medium)
Solution: Topological Sort
Alien Dictionary (hard)
Solution: Alien Dictionary
Problem Challenge 1: Reconstructing a Sequence (hard)
Solution: Problem Challenge 1: Reconstructing a Sequence
Problem Challenge 2: Minimum Height Trees (hard)
Solution: Problem Challenge 2: Minimum Height Trees
Introduction to Union Find Pattern
Redundant Connection (medium)
Solution: Redundant Connection
Number of Provinces (medium)
Solution: Number of Provinces
Is Graph Bipartite? (medium)
Solution: Is Graph Bipartite?
Path With Minimum Effort (medium)
Solution: Path With Minimum Effort
Introduction to Ordered Set Pattern
Merge Similar Items (easy)
Solution: Merge Similar Items
132 Pattern (medium)
Solution: 132 Pattern
My Calendar I (medium)
Solution: My Calendar I
Longest Continuous Subarray (medium)
Solution: Longest Continuous Subarray
Introduction Prefix Sum Pattern
Find the Middle Index in Array (easy)
Solution: Find the Middle Index in Array
Left and Right Sum Differences (easy)
Solution: Left and Right Sum Differences (easy)
Maximum Size Subarray Sum Equals k (medium)
Solution: Maximum Size Subarray Sum Equals k
Binary Subarrays With Sum (medium)
Solution: Binary Subarrays With Sum
Subarray Sums Divisible by K (medium)
Solution: Subarray Sums Divisible by K
Sum of Absolute Differences in a Sorted Array (medium)
Solution: Sum of Absolute Differences in a Sorted Array
Subarray Sum Equals K (medium)
Solution: Subarray Sum Equals K
Same Tree (medium)
Solution: Same Tree
Invert Binary Tree (medium)
Solution: Invert Binary Tree
Binary Search Tree Iterator (medium)
Solution: Binary Search Tree Iterator
Kth Smallest Number (hard)
Solution: Kth Smallest Number
Coding Patterns: A Cheat Sheet
Introduction
Two Sum (easy)
Solution: Two Sum
Valid Perfect Square (easy)
Solution: Valid Perfect Square
Best Time to Buy and Sell (easy)
Solution: Best Time to Buy and Sell Stock
Valid Parentheses (Easy)
Solution: Valid Parentheses
Subtree of Another Tree (easy)
Solution: Subtree of Another Tree
Daily Temperatures (medium)
Solution: Daily Temperatures
Group Anagrams (medium)
Solution: Group Anagrams
Decode String (medium)
Solution: Decode String
Valid Sudoku (medium)
Solution: Valid Sudoku
Product of Array Except Self (medium)
Solution: Product of Array Except Self
Maximum Product Subarray (medium)
Solution: Maximum Product Subarray
Container With Most Water (medium)
Solution: Container With Most Water
Palindromic Substrings (medium)
Solution: Palindromic Substrings
Remove Nth Node From End of List (medium)
Solution: Remove Nth Node From End of List
Find Minimum in Rotated Sorted Array (medium)
Solution: Find Minimum in Rotated Sorted Array
Pacific Atlantic Water Flow (medium)
Solution: Pacific Atlantic Water Flow
Validate Binary Search Tree (medium)
Solution: Validate Binary Search Tree
Construct Binary Tree from Preorder and Inorder Traversal (medium)
Solution: Construct Binary Tree from Preorder and Inorder Traversal
Clone Graph (medium)
Solution: Clone Graph
House Robber II (medium)
Solution: House Robber II
Decode Ways (medium)
Solution: Decode Ways
Unique Paths (medium)
Solution: Unique Paths
Word Break (medium)
Solution: Word Break
Lowest Common Ancestor of a Binary Search Tree (medium)
Solution: Lowest Common Ancestor of a Binary Search Tree
Longest Consecutive Sequence (medium)
Solution: Longest Consecutive Sequence
Meeting Rooms II (medium)
Solution: Meeting Rooms II
Encode and Decode Strings
Solution: Encode and Decode Strings
Number of Connected Components in an Undirected Graph
Solution: Number of Connected Components in an Undirected Graph
Graph Valid Tree (medium)
Solution: Graph Valid Tree
Implement Trie (Prefix Tree) (medium)
Solution: Implement Trie (Prefix Tree)
Design Add and Search Words Data Structure (medium)
Solution: Design Add and Search Words Data Structure
Longest Valid Parentheses (hard)
Solution: Longest Valid Parentheses
Serialize and Deserialize Binary Tree (hard)
Solution: Serialize and Deserialize Binary Tree
Where to Go from Here
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