Data Structures and Algorithms Introduction | Hello Interview
Learn DSA Through Visualizations
A visual guide to the most important patterns and approaches for the coding interview.
This guide uses interactive visualizations to teach you the most important algorithm patterns for the coding interview.
| Done | Problem / Lesson | Difficulty |
|---|---|---|
| ###### Two Pointers (7 problems) 0% |
Lesson | |
| Container With Most Water | Medium | |
| Two Sum (Sorted Array) | Medium | |
| 3-Sum | Medium | |
| Triangle Numbers | Medium | |
| Move Zeroes | Easy | |
| Sort Colors | Medium | |
| Trapping Rain Water | Hard | |
| ###### Sliding Window (5 problems) 0% |
Lesson | |
| Maximum Sum of Subarrays of Size K | Easy | |
| Max Points You Can Obtain From Cards | Medium | |
| Max Sum of Distinct Subarrays Length k | Medium | |
| Longest Substring Without Repeating Characters | Medium | |
| Longest Repeating Character Replacement | Medium | |
| ###### Intervals (5 problems) 0% |
Lesson | |
| Can Attend Meetings | Easy | |
| Insert Interval | Medium | |
| Non-Overlapping Intervals | Medium | |
| Merge Intervals | Medium | |
| Employee Free Time | Hard | |
| ###### Stack (5 problems) 0% |
Lesson | |
| Valid Parentheses | Easy | |
| Decode String | Medium | |
| Longest Valid Parentheses | Hard | |
| Daily Temperatures | Medium | |
| Largest Rectangle in Histogram | Hard | |
| ###### Linked List (5 problems) 0% |
Lesson | |
| Linked List Cycle | Easy | |
| Palindrome Linked List | Easy | |
| Remove Nth Node From End of List | Medium | |
| Reorder List | Medium | |
| Swap Nodes in Pairs | Medium | |
| ###### Binary Search (2 problems) 0% |
Lesson | |
| Apple Harvest (Koko Eating Bananas) | Medium | |
| Search in Rotated Sorted Array | Medium | |
| ###### Heap (4 problems) 0% |
Lesson | |
| Kth Largest Element in an Array | Medium | |
| K Closest Points to Origin | Medium | |
| Find K Closest Elements | Medium | |
| Merge K Sorted Lists | Hard | |
| ###### Depth-First Search (13 problems) 0% |
Lesson | |
| Maximum Depth of Binary Tree | Easy | |
| Path Sum | Easy | |
| Validate Binary Search Tree | Medium | |
| Calculate Tilt | Easy | |
| Diameter of a Binary Tree | Easy | |
| Path Sum II | Medium | |
| Longest Univalue Path | Medium | |
| Copy Graph | Easy | |
| Graph Valid Tree | Medium | |
| Flood Fill | Easy | |
| Number of Islands | Medium | |
| Surrounded Regions | Medium | |
| Pacific Atlantic Water Flow | Medium | |
| ###### Breadth-First Search (8 problems) 0% |
Lesson | |
| Level Order Sum | Easy | |
| Rightmost Node | Medium | |
| Zigzag Level Order | Medium | |
| Maximum Width of Binary Tree | Medium | |
| Minimum Knight Moves | Medium | |
| Rotting Oranges | Medium | |
| 01-Matrix | Medium | |
| Bus Routes | Hard | |
| ###### Backtracking (4 problems) 0% |
Lesson | |
| Word Search | Medium | |
| Subsets | Medium | |
| Generate Parentheses | Medium | |
| Combination Sum | Medium | |
| ###### Graphs (2 problems) 0% |
Lesson | |
| Course Schedule | Medium | |
| Course Schedule II | Medium | |
| ###### Dynamic Programming (7 problems) 0% |
Lesson | |
| Counting Bits | Easy | |
| Decode Ways | Medium | |
| Unique Paths | Medium | |
| Maximal Square | Medium | |
| Longest Increasing Subsequence | Medium | |
| Word Break | Medium | |
| Maximum Profit in Job Scheduling | Medium | |
| ###### Greedy Algorithms (3 problems) 0% |
Lesson | |
| Best Time to Buy and Sell Stock | Easy | |
| Gas Station | Medium | |
| Jump Game | Medium | |
| ###### Trie (2 problems) 0% |
Lesson | |
| Implement Trie Methods | Medium | |
| Prefix Matching | Medium | |
| ###### Prefix Sum (2 problems) 0% |
Lesson | |
| Count Vowels in Substrings | Medium | |
| Subarray Sum Equals K | Medium | |
| ###### Matrices (3 problems) 0% |
Lesson | |
| Spiral Matrix | Medium | |
| Rotate Image | Medium | |
| Set Matrix Zeroes | Medium |