30-Day-Challenge-CPP

Refer to this video before starting this challenge

Thank you take U forward for the list of practice questions.

The solutions will be included but if you want to search or practice for different solution, search the question in leetcode and geeksforgeeks. The links for leetcode questions will be given in comments in the solution of the question.

If you have not set up your working environment, refer to this video.

To directly run the code given, change input.txt to give your input and keep the folders and file as they are. The solutions given can be run on gcc_14 or above compilers.

Day 1 -> Arrays

1. Find the duplicate in an array of N integers
2. Sort an array of 0s, 1s and 2s without using extra space or sorting algorithm
3. Find missing number from array of N - 1 numbers that have the range of [0, N]
4. Merge two sorted array without extra space
5. Kadane's algorithm
6. Merge overlapping intervals

Day 2 -> Arrays

1. Set matrix zeroes
2. Pascal triangle
3. Next permutation
4. Count inversions using merge sort
5. Maximum stock profit
6. Rotate matrix 90 degrees

Day 3 -> Maths

1. Excel Column Number
2. Find n^x in log N
3. Count trailing zeros in factorial of a number
4. Find GCD in Log N
5. Grid Unique Paths
6. GCD of strings
7. Go through Puzzles from GFG (Search on own)

Day 4 -> Hashing

1. 2 Sum problem
2. 4 Sum problem
3. Longest Consecutive Sequence
4. Longest Subarray with 0 sum
5. Count number of subarrays with given XOR(this clears a lot of problems)
6. Longest substring without repeat

Day 5 -> Linked List

1. Reverse a LinkedList
2. Find middle of LinkedList
3. Merge two sorted Linked List
4. Remove N-th node from back of LinkedList
5. Delete a given Node when a node is given. (0(1) solution)
6. Add two numbers as LinkedList

Day 6 -> Linked List

1. Find intersection point of Y LinkedList
2. Check if a LinkedList is palindrome or not.
3. Reverse a LinkedList in groups.
4. Detect a cycle and removing loop(two different questions and same concept)
5. Flattening of a LinkedList
6. Rotate a LinkedList
7. Clone a Linked List with random and next pointer

Day 7 -> 2 - Pointer

1. Merge two sorted LinkedLists
2. Find the starting point of the loop.
3. 3 sum
4. Trapping rainwater
5. Remove Duplicate from Sorted array
6. Max continuous number of 1’s

Day 8 -> Greedy

1. N meeting in one room
2. Activity Selection
3. Greedy algorithm to find minimum number of coins
4. Fractional Knapsack Problem
5. Minimum number of platforms required for a railway
6. Job sequencing Problem

Day 9 -> Backtracking

1. N queens Problem
2. Sudoko
3. M coloring Problem
4. Rat in a Maze
5. Print all Permutations of a string/array
6. Word Break (print all ways)

Day 10 -> Backtracking

1. Combination sum-1
2. Combination sum-2
3. Palindrome Partioning
4. Subset Sum
5. K-th permutation Sequence

Day 11 -> Divide and Conquer

1. 1/N-th root of an integer (use binary search) (square root, cube root, ..)
2. Matrix Median
3. Find the element that appears once in sorted array, and rest element appears twice (Binary search)
4. Search element in a sorted and rotated array.
5. K-th element of two sorted arrays
6. Media of an array

Day 12 -> Bits

1. Check if a number if a power of 2 or not in O(1)
2. Count total set bits
3. Divide Integers without / operator
4. Power Set (this is very important)
5. Find MSB in o(1)
6. Find square of a number without using multiplication or division operators.

Day 13 -> Stack and Queue

1. Implement Stack
2. Implement Queue
3. BFS
4. Implement Stack using Queue
5. Implement Queue using Stack
6. Check for balanced parentheses
7. Next Greater Element

Day 14 -> Stack and Queue

1. Next Smaller Element
2. LRU cache (vvvv. imp)
3. Largest rectangle in histogram
4. Sliding Window maximum
5. Implement Min Stack
6. Rotten Orange (Using BFS)

Day 15 -> String

1. Reverse Words in a String
2. Longest Palindrome in a string
3. Roman Number to Integer and vice versa
4. Implement ATOI/STRSTR
5. Longest Common Prefix
6. Rabin Karp

Day 16 -> String

1. Prefix Function/Z-Function
2. KMP algo
3. Minimum characters needed to be inserted in the beginning to make it palindromic.
4. Check for Anagrams
5. Count and Say
6. Compare version numbers

Day 17 -> Binary Tree

1. Insertion and Deletion in Binary Tree.
2. Inorder Traversal (with recursion and without recursion)
3. Preorder Traversal (with recursion and without recursion)
4. Postorder Traversal (with recursion and without recursion)
5. LeftView Of Binary Tree
6. Bottom View of Binary Tree
7. Top View of Binary Tree

Day 18 -> Binary Tree

1. Level order Traversal / Level order traversal in spiral form
2. Height of a Binary Tree
3. Diameter of Binary Tree
4. Check if Binary tree is height balanced or not
5. LCA in Binary Tree
6. Check if two trees are identical or not

Day 19 -> Binary Tree

1. Maximum path sum
2. Construct Binary Tree from inorder and preorder
3. Construct Binary Tree from Inorder and Postorder
4. Symmetric Binary Tree/Mirror of itself or not
5. Flatten Binary Tree to LinkedList

Day 20 -> Binary Search Tree

1. Insert and Delete in BST
2. Populate Next Right pointers of Tree
3. Search given Key in BST
4. Check if a BT is BST or not
5. Find LCA of two nodes in BST
6. Find the inorder predecessor/successor of a given Key in BST.

Day 21 -> Binary Search Tree

1. Floor and Ceil in a BST
2. Find K-th smallest and K-th largest element in BST (2 different Questions)
3. Find a pair with a given sum in BST
4. BST iterator
5. Size of the largest BST in a Binary Tree
6. Serialize and deserialize Binary Tree

Day 22 -> Mixed Questions

1. Binary Tree to Double Linked List
2. Find median in a stream of running integers.
3. K-th largest element in a stream.
4. Distinct numbers in Window.
5. K-th largest element in an unsorted array.
6. Flood-fill Algorithm

Day 23 -> Graph

1. Clone a graph (Not that easy as it looks)
2. DFS
3. BFS
4. Detect A cycle in Undirected Graph/Directed Graph
5. Topo Sort
6. Number of islands (Do in Grid and Graph both)
7. Bipartite Check

Day 24 -> Graph

1. SCC(using KosaRaju’s algo)
2. Dijkstra’s Algorithm
3. Bellman Ford Algo
4. Floyd Warshall Algorithm
5. MST using Prim’s Algo
6. MST using Kruskal’s Algo

Day 25 -> Dynamic Programming

1. Max Product Subarray
2. Longest Increasing Subsequence
3. Longest Common Subsequence
4. 0-1 Knapsack
5. Edit Distance
6. Maximum sum increasing subsequence
7. Matrix Chain Multiplication

Day 26 -> Dynamic Programming

1. Maximum sum path in matrix, (count paths, and similar type do, also backtrack to find the maximum path)
2. Coin change
3. Subset Sum
4. Rod Cutting
5. Egg Dropping
6. Word Break
7. Palindrome Partitioning (MCM Variation)

Now the revision of important subject starts

Day 27 -> Operating System

1. Revise OS notes that you would have made during your semester.
2. If not made notes, spend 2 to 3 days and make notes from Knowledge Gate.

Day 28 -> Database Management System

1. Revise DBMS notes that you would have made during your semester.
2. If not made notes, spend 2 to 3 days and make notes from Knowledge Gate.

Day 29 -> Computer Networks

1. Revise CN notes that you would have made during your semester.
2. If not made notes, spend 2 to 3 days and make notes from Knowledge Gate.

Day 30 -> Your Projects And Its Presentation

1. Make a note of how you will represent your projects, and prepare all questions related to technology which you have used in your projects. Prepare a note which you can say for 3-10 minutes when they asks you that say something about your projects.

Bonus Days -> Revise OOP Concepts

1. Revise OOP using Java or CPP or Python. Learn how to make templates and libraries/packages.
2. Learn DSU(Disjoint Set Union) Datastructure.