Tech-Notes

Striver’s SDE Sheet

  1. Arrays
  2. Arrays Part-II
  3. Arrays Part-III
  4. Arrays Part-IV
  5. Linked List
  6. Linked List Part-II
  7. Linked List and Arrays
  8. Greedy Algorithm
  9. Recursion
  10. Recursion and Backtracking
  11. Binary Search
  12. Heaps
  13. Stack and Queue
  14. Stack and Queue Part-II
  15. String
  16. String Part-II
  17. Binary Tree
  18. Binary Tree Part-II
  19. Binary Tree Part-III
  20. Binary Search Tree
  21. Binary Search Tree Part-II
  22. Binary Trees [Miscellaneous]
  23. Graph
  24. Graph Part-II
  25. Dynamic Programming
  26. Dynamic Programming Part-II
  27. Trie )

Day 1: Arrays

# Problem Level Status LeetCode Link Answer
1 Set Matrix Zeros Medium ❌ LeetCode  
2 Pascal’s Triangle Medium ❌ LeetCode  
3 Next Permutation Medium ❌ LeetCode  
4 Kadane’s Algorithm Easy ❌ LeetCode  
5 Sort an array of 0’s, 1’s and 2’s Medium ❌ LeetCode  
6 Stock Buy and Sell Easy ❌ LeetCode  

Day 2: Arrays Part-II

# Problem Level Status LeetCode Link Answer
1 Rotate Matrix Medium ❌ LeetCode  
2 Merge Overlapping Subintervals Medium ❌ LeetCode  
3 Merge two sorted arrays without extra space Medium ❌ LeetCode  
4 Find the duplicate in an array of N+1 integers Medium ❌ LeetCode  
5 Repeat and Missing Number Hard ❌ LeetCode  
6 Inversion of Array (Pre-req: Merge Sort) Medium ❌ LeetCode  

Day 3: Arrays Part-III

# Problem Level Status LeetCode Link Answer
1 Search in a 2 D matrix Medium ❌ LeetCode  
2 Pow(x, n) Medium ❌ LeetCode  
3 Majority Element (>n/2 times) Easy ❌ LeetCode  
4 Majority Element (n/3 times) Medium ❌ LeetCode  
5 Grid Unique Paths Medium ❌ LeetCode  
6 Reverse Pairs (Leetcode) Medium ❌ LeetCode  

Day 4: Arrays Part-IV

# Problem Level Status LeetCode Link Answer
1 2Sum Problem Medium ❌ LeetCode  
2 4-Sum Problem Hard ❌ LeetCode  
3 Longest Consecutive Sequence Medium ❌ LeetCode  
4 Largest Subarray with K sum Medium ❌ LeetCode  
5 Count number of subarrays with given xor K Hard ❌ LeetCode  
6 Longest Substring without repeat Medium ❌ LeetCode  

Day 5: Linked List

# Problem Level Status LeetCode Link Answer
1 Reverse a LinkedList Easy ❌ LeetCode  
2 Find the middle of LinkedList Easy ❌ LeetCode  
3 Merge two sorted Linked List (use method used in mergeSort) Medium ❌ LeetCode  
4 Remove N-th node from back of LinkedList Medium ❌ LeetCode  
5 Add two numbers as LinkedList Medium ❌ LeetCode  
6 Delete a given Node when a node is given.(O(1) solution) Medium ❌ LeetCode  

Day 6: Linked List Part-II

# Problem Level Status LeetCode Link Answer
1 Find intersection point of Y LinkedList Medium ❌ LeetCode  
2 Detect a cycle in Linked List Medium ❌ LeetCode  
3 Reverse a LinkedList in groups of size k Hard ❌ LeetCode  
4 Check if a LinkedList is palindrome or not Medium ❌ LeetCode  
5 Find the starting point of the Loop of LinkedList Medium ❌ LeetCode  
6 Flattening of a LinkedList Medium ❌ LeetCode  

Day 7: Linked List and Arrays

# Problem Level Status LeetCode Link Answer
1 Rotate a LinkedList Medium ❌ LeetCode  
2 Clone a Linked List with random and next pointer Hard ❌ LeetCode  
3 3 sum Medium ❌ LeetCode  
4 Trapping Rainwater Hard ❌ LeetCode  
5 Remove Duplicate from Sorted array Easy ❌ LeetCode  
6 Max consecutive ones Easy ❌ LeetCode  

Day 8: Greedy Algorithm

# Problem Level Status LeetCode Link Answer
1 N meetings in one room Medium ❌ LeetCode  
2 Minimum number of platforms required for a railway Medium ❌ LeetCode  
3 Job sequencing Problem Medium ❌ LeetCode  
4 Fractional Knapsack Problem Medium ❌ LeetCode  
5 Greedy algorithm to find minimum number of coins Medium ❌ LeetCode  
6 Assign Cookies Medium ❌ LeetCode  

Day 9: Recursion

# Problem Level Status LeetCode Link Answer
1 Subset Sums Medium ❌ LeetCode  
2 Subset-II Medium ❌ LeetCode  
3 Combination sum-1 Medium ❌ LeetCode  
4 Combination sum-2 Medium ❌ LeetCode  
5 Palindrome Partitioning Medium ❌ LeetCode  
6 K-th permutation Sequence Medium ❌ LeetCode  

Day 10: Recursion and Backtracking

# Problem Level Status LeetCode Link Answer
1 Print all permutations of a string/array Medium ❌ LeetCode  
2 N queens Problem Hard ❌ LeetCode  
3 Sudoku Solver Hard ❌ LeetCode  
4 M Coloring Problem Hard ❌ LeetCode  
5 Rat in a Maze Hard ❌ LeetCode  
6 Word Break (print all ways) Medium ❌ LeetCode  
# Problem Level Status LeetCode Link Answer
1 The N-th root of an integer Easy ❌ LeetCode  
2 Matrix Median Hard ❌ LeetCode  
3 Find the element that appears once in a sorted array, and the rest element appears twice (Binary search) Medium ❌ LeetCode  
4 Search element in a sorted and rotated array/ find pivot where it is rotated Medium ❌ LeetCode  
5 Median of 2 sorted arrays Hard ❌ LeetCode  
6 K-th element of two sorted arrays Medium ❌ LeetCode  
7 Allocate Minimum Number of Pages Hard ❌ LeetCode  
8 Aggressive Cows Medium ❌ LeetCode  

Day 12: Heaps

# Problem Level Status LeetCode Link Answer
1 Max heap, Min Heap Implementation (Only for interviews) Medium ❌ LeetCode  
2 Kth Largest Element Easy ❌ LeetCode  
3 Maximum Sum Combination Medium ❌ LeetCode  
4 Find Median from Data Stream Hard ❌ LeetCode  
5 Merge K sorted arrays Medium ❌ LeetCode  
6 K most frequent elements Medium ❌ LeetCode  

Day 13: Stack and Queue

# Problem Level Status LeetCode Link Answer
1 Implement Stack using Arrays Easy ❌ LeetCode  
2 Implement Queue using Arrays Easy ❌ LeetCode  
3 Implement Stack using Queue (using single queue) Medium ❌ LeetCode  
4 Implement Queue using Stack (O(1) amortized method) Medium ❌ LeetCode  
5 Check for balanced parentheses Medium ❌ LeetCode  
6 Next Greater Element Easy ❌ LeetCode  
7 Sort a Stack Medium ❌ LeetCode  

Day 14: Stack and Queue Part-II

# Problem Level Status LeetCode Link Answer
1 Next Smaller Element Easy ❌ LeetCode  
2 LRU cache (IMPORTANT) Hard ❌ LeetCode  
3 LFU cache Hard ❌ LeetCode  
4 Largest rectangle in a histogram Medium ❌ LeetCode  
5 Sliding Window Maximum Hard ❌ LeetCode  
6 Implement Min Stack Medium ❌ LeetCode  
7 Rotten Orange (Using BFS) Medium ❌ LeetCode  
8 Stock Span Problem Medium ❌ LeetCode  
9 Find the maximum of minimums of every window size Medium ❌ LeetCode  
10 The Celebrity Problem Medium ❌ LeetCode  

Day 15: String

# Problem Level Status LeetCode Link Answer
1 Reverse Words in a String Easy ❌ LeetCode  
2 Longest Palindrome in a string Medium ❌ LeetCode  
3 Roman Number to Integer and vice versa Easy ❌ LeetCode  
4 Implement ATOI/STRSTR Medium ❌ LeetCode  
5 Longest Common Prefix Easy ❌ LeetCode  
6 Rabin Karp ❓ ❌ LeetCode  

Day 16: String Part-II

# Problem Level Status LeetCode Link Answer
1 Z-Function Easy ❌ LeetCode  
2 KMP Algo / LPS(pi) Array Hard ❌ LeetCode  
3 Minimum characters needed to be inserted in the beginning to make it palindromic Hard ❌ LeetCode  
4 Check for Anagrams Easy ❌ LeetCode  
5 Count and Say Medium ❌ LeetCode  
6 Compare Version Numbers Easy ❌ LeetCode  

Day 17: Binary Tree

# Problem Level Status LeetCode Link Answer
1 Inorder Traversal Easy ❌ LeetCode  
2 Preorder Traversal Easy ❌ LeetCode  
3 Postorder Traversal Easy ❌ LeetCode  
4 Morris Inorder Traversal Medium ❌ LeetCode  
5 Morris Preorder Traversal Medium ❌ LeetCode  
6 LeftView Of Binary Tree Easy ❌ LeetCode  
7 Bottom View of Binary Tree Medium ❌ LeetCode  
8 Top View of Binary Tree Easy ❌ LeetCode  
9 Preorder, inorder, postorder in a single traversal Medium ❌ LeetCode  
10 Vertical order traversal Easy ❌ LeetCode  
11 Root to Node Path in Binary Tree Medium ❌ LeetCode  
12 Max width of a Binary Tree Medium ❌ LeetCode  

Day 18: Binary Tree Part-II

# Problem Level Status LeetCode Link Answer
1 Level order Traversal / Level order traversal in spiral form Easy ❌ LeetCode  
2 Height of a Binary Tree Medium ❌ LeetCode  
3 Diameter of Binary Tree Medium ❌ LeetCode  
4 Check if the Binary tree is height-balanced or not Medium ❌ LeetCode  
5 LCA in Binary Tree Medium ❌ LeetCode  
6 Check if two trees are identical or not Medium ❌ LeetCode  
7 Zig Zag Traversal of Binary Tree Easy ❌ LeetCode  
8 Boundary Traversal of Binary Tree Medium ❌ LeetCode  

Day 19: Binary Tree Part-III

# Problem Level Status LeetCode Link Answer
1 Maximum path sum Hard ❌ LeetCode  
2 Construct Binary Tree from inorder and preorder Hard ❌ LeetCode  
3 Construct Binary Tree from Inorder and Postorder Hard ❌ LeetCode  
4 Symmetric Binary Tree Medium ❌ LeetCode  
5 Flatten Binary Tree to LinkedList Hard ❌ LeetCode  
6 Check if Binary Tree is the mirror of itself or not Medium ❌ LeetCode  
7 Check for Children Sum Property Medium ❌ LeetCode  

Day 20: Binary Search Tree

# Problem Level Status LeetCode Link Answer
1 Populate Next Right pointers of Tree Medium ❌ LeetCode  
2 Search given Key in BST Easy ❌ LeetCode  
3 Construct BST from given keys Hard ❌ LeetCode  
4 Construct a BST from a preorder traversal Medium ❌ LeetCode  
5 Check if a BT is BST or not Medium ❌ LeetCode  
6 Find LCA of two nodes in BST Medium ❌ LeetCode  
7 Find the inorder predecessor/successor of a given Key in BST Medium ❌ LeetCode  

Day 21: Binary Search Tree Part-II

# Problem Level Status LeetCode Link Answer
1 Floor in a BST Easy ❌ LeetCode  
2 Ceil in a BST Easy ❌ LeetCode  
3 Find K-th smallest element in BST Medium ❌ LeetCode  
4 Find K-th largest element in BST Medium ❌ LeetCode  
5 Find a pair with a given sum in BST Medium ❌ LeetCode  
6 BST iterator Medium ❌ LeetCode  
7 Size of the largest BST in a Binary Tree Medium ❌ LeetCode  
8 Serialize and deserialize Binary Tree Medium ❌ LeetCode  

Day 22: Binary Trees [Miscellaneous]

# Problem Level Status LeetCode Link Answer
1 Binary Tree to Double Linked List Medium ❌ LeetCode  
2 Find median in a stream of running integers. Hard ❌ LeetCode  
3 K-th largest element in a stream. Easy ❌ LeetCode  
4 Distinct numbers in Window. Medium ❌ LeetCode  
5 K-th largest element in an unsorted array. Easy ❌ LeetCode  
6 Flood-fill Algorithm Medium ❌ LeetCode  

Day 23: Graph

# Problem Level Status LeetCode Link Answer
1 Clone a graph (Not that easy as it looks) Hard ❌ LeetCode  
2 DFS Hard ❌ LeetCode  
3 BFS Medium ❌ LeetCode  
4 Detect A cycle in Undirected Graph using BFS Hard ❌ LeetCode  
5 Detect A cycle in Undirected Graph using DFS Hard ❌ LeetCode  
6 Detect A cycle in a Directed Graph using DFS Hard ❌ LeetCode  
7 Detect A cycle in a Directed Graph using BFS Hard ❌ LeetCode  
8 Topological Sort BFS Hard ❌ LeetCode  
9 Topological Sort DFS Hard ❌ LeetCode  
10 Number of islands (Do in Grid and Graph Both) Hard ❌ LeetCode  
11 Bipartite Check using BFS Medium ❌ LeetCode  
12 Bipartite Check using DFS Hard ❌ LeetCode  

Day 24: Graph Part-II

# Problem Level Status LeetCode Link Answer
1 Strongly Connected Component (using KosaRaju’s algo) Hard ❌ LeetCode  
2 Dijkstra’s Algorithm Hard ❌ LeetCode  
3 Bellman-Ford Algo Hard ❌ LeetCode  
4 Floyd Warshall Algorithm Hard ❌ LeetCode  
5 MST using Prim’s Algo Hard ❌ LeetCode  
6 MST using Kruskal’s Algo Hard ❌ LeetCode  

Day 25: Dynamic Programming

# Problem Level Status LeetCode Link Answer
1 Max Product Subarray Medium ❌ LeetCode  
2 Longest Increasing Subsequence Medium ❌ LeetCode  
3 Longest Common Subsequence Medium ❌ LeetCode  
4 0-1 Knapsack Medium ❌ LeetCode  
5 Edit Distance Hard ❌ LeetCode  
6 Maximum Sum Increasing Subsequence Hard ❌ LeetCode  
7 Matrix Chain Multiplication Hard ❌ LeetCode  

Day 26: Dynamic Programming Part-II

# Problem Level Status LeetCode Link Answer
1 Minimum Sum Path in the Matrix (count paths and similar types, also backtrack to find the Minimum path) Medium ❌ LeetCode  
2 Coin Change Hard ❌ LeetCode  
3 Subset Sum Medium ❌ LeetCode  
4 Rod Cutting Hard ❌ LeetCode  
5 Egg Dropping Hard ❌ LeetCode  
6 Word Break Medium ❌ LeetCode  
7 Palindrome Partitioning (MCM Variation) Hard ❌ LeetCode  
8 Maximum Profit in Job Scheduling Hard ❌ LeetCode  

Day 27: Trie

# Problem Level Status LeetCode Link Answer
1 Implement Trie (Prefix Tree) Hard ❌ LeetCode  
2 Implement Trie - 2 (Prefix Tree) Hard ❌ LeetCode  
3 Longest String with All Prefixes Medium ❌ LeetCode  
4 Number of Distinct Substrings in a String Hard ❌ LeetCode  
5 Power Set (this is very important) Medium ❌ LeetCode  
6 Maximum XOR of two numbers in an array Medium ❌ LeetCode  
7 Maximum XOR With an Element From Array Hard ❌ LeetCode