📌 1. Arrays (Easy → Hard)
🟢 Easy (Available on LeetCode / GFG / HackerRank / InterviewBit)
- Second Largest Element (GFG)
- Third Largest Element (GFG)
- Max Consecutive Ones (LeetCode / GFG)
- Reverse Array in Groups (GFG)
- Wave Array (GFG)
- Repetitive Addition of Digits (GFG)
- Remove All Occurrences of Element (GFG)
- Alternate Positive Negative (GFG)
- Array Leaders (GFG)
- Missing & Repeating Number (GFG)
- Missing Ranges of Numbers (GFG)
- Plus One (LeetCode / GFG)
- Remove Duplicates from Sorted Array (LeetCode / GFG)
- Two Sum (LeetCode / InterviewBit)
- Move Zeros to End (LeetCode / GFG)
- Rotate Array (LeetCode / InterviewBit)
- Maximum Consecutive Ones (LeetCode / GFG)
- Intersection of Two Arrays (LeetCode)
- Remove Element (LeetCode)
🟡 Medium & Hard
(Same as previous; journeys from Merge Intervals, Trapping Rain Water, etc.)
2. Strings (Easy → Hard)
🟢 Easy (LeetCode / GFG / HackerRank)
- Anagram Check (GFG / LeetCode)
- Valid Parentheses (LeetCode)
- Reverse Words in a String (LeetCode)
- Longest Common Prefix (LeetCode)
- String Compression (LeetCode)
- Count and Say (LeetCode)
- Valid Palindrome (LeetCode)
- First Unique Character (LeetCode)
- Implement strStr() (Needle in a Haystack) (LeetCode)
- Reverse String (LeetCode)
3. Linked Lists (Easy → Hard)
🟢 Easy (LeetCode / GFG / InterviewBit)
- Reverse a Linked List (LeetCode)
- Detect Cycle (LeetCode)
- Merge Two Sorted Lists (LeetCode)
- Find Middle of Linked List (LeetCode)
- Delete Node Without Head Pointer (GFG)
- Remove Linked List Elements (LeetCode)
- Linked List Cycle II (LeetCode)
- Delete Node in a Linked List (LeetCode)
- Merge Two Sorted Linked Lists (InterviewBit/LeetCode)
4. Stacks & Queues (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Valid Parentheses
- Min Stack
- Stack using Queues
- Queue using Stacks
- Evaluate Reverse Polish Notation (LeetCode / GFG)
- Circular Queue Implementation (GFG)
5. Trees (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Inorder, Preorder, Postorder Traversal (LeetCode)
- Level Order Traversal (LeetCode)
- Balanced Binary Tree (LeetCode)
- Left/Right View of Tree (GFG)
- Maximum & Minimum Depth of Binary Tree (LeetCode)
6. Graphs (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- BFS & DFS Traversal (LeetCode)
- Number of Islands (LeetCode)
- Flood Fill (LeetCode)
- Clone Graph (LeetCode)
- Graph Valid Tree (LeetCode)
- Find if Path Exists in Graph (LeetCode)
7. Recursion & Backtracking (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Fibonacci (Recursion)
- Subsets (LeetCode)
- Permutations (LeetCode)
- Rat in a Maze (GFG)
- Power Set (GFG / LeetCode)
- Count Ways – small n Coin Change (LeetCode / GFG)
8. Searching & Sorting (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Binary Search (LeetCode)
- Insertion, Bubble, Selection Sort (GFG)
- Sort Array (LeetCode)
- Square Root Calculation (GFG / LeetCode)
9. Dynamic Programming (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Min Cost Climbing Stairs (LeetCode)
- House Robber (LeetCode)
- Decode Ways (LeetCode)
- Unique Paths (LeetCode)
- Climbing Stairs (LeetCode)
- Maximum Subarray (Kadane) (LeetCode)
- Best Time to Buy and Sell Stock (LeetCode)
10. Bit Manipulation (Easy → Hard)
🟢 Easy (LeetCode / GFG)
- Single Number (LeetCode)
- Power of Two (LeetCode)
- Count Set Bits / Hamming Weight (LeetCode / GFG)
- XOR of All Elements (Common Practice)
- Is Power of Two (LeetCode)
- Hamming Distance (LeetCode)
Common Platforms for Practice
You can find these problems on:
- GeeksforGeeks — comprehensive tutorials and interview topics
- LeetCode — curated problems and mock interview environment
- HackerRank — multi-language challenges and certifications
- Codeforces, CodeChef — competitive programming contests and practice
- InterviewBit — structured interview prep path
- SPOJ, TopCoder, AtCoder, HackerEarth, Exercism, Edabit — varied problem styles
Happy Coding! 🚀
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