C++/Java/Python. Make sure that you are comfortable with the basic concepts of programming.

Things to do :

• Things to Know in C++/Java/Python or any language.
  → User Input/Output.
  → Data Types
  → If Else statement
  → Switch Statement
  → Arrays, Strings
  → For Loop
  → While Loop
  → Function
  → Time Complexity

• Build up Logical Thinking.
  → Practice Pattern Questions from any source like Leetcode.

• Learn STL/Java-Collections or similar things in your language.

• Basic Maths.
  → Count Digits
  → Reverse a Number
  → Check Palindrome
  → GCD or HCF
  → Armstrong Number
  → Print all Divisors
  → Check for Prime

  

• Learn Basic Recursion.
  → Understand recursion by printing something N times
  → Print name N times using recursion
  → Print 1 to N using recursion
  → Print N to 1 using recursion
  → Sum of first N numbers
  → Factorial of N numbers
  → Reverse an array
  → Check if a string is a palindrome or not
  → Fibonacci Number

• Learn Basic Hashing.
  → Counting frequencies of array elements
  → Find the highest/lowest frequency element

Day 1 to 10: Sorting

Things to do:

• Selection Sort

• Bubble Sort

• Insertion Sort

• Merge Sort

• Quick Sort

• Cycle Sort

• Heap Sort

Day 11–25: Binary Search

Things to do:

• Binary Search on 1D Arrays

→ Binary Search to find X in Sorted Array
→ Lower Bound and Upper Bound
→ Search Insert Position
→ Check if the Input array is sorted
→ Find the first and last occurrence of a given number in a sorted array
→ Count the occurrence of a number in a sorted array with duplicates
→ Find peak element
→ Search in Rotated Sorted Array I
→ Search in Rotated Sorted Array II
→ Find Minimum in Rotated Sorted Array
→ Single element in a sorted Array
→ Find the kth element of two sorted arrays
→ Find out how many times has an array been rotated
→ Order-Agnostic Binary Search

• Binary Search on 2D Arrays
  → Search in a 2D matrix
  → Find the Peak Element
  → Matrix Median

• Find Answers by Binary Search in Search Space
  → Find the square root of a number in log n
  → Find the Nth root of a number using BS
  → Koko Eating Bananas
  → Minimum days to make M bouquets
  → Find the smallest Divisor
  → Capacity to Ship Packages within D Days
  → Median of two sorted arrays
  → Aggressive Cows
  → Book Allocation Problem
  → Split array-Largest Sum
  → Kth Missing Positive number
  → Minimize Max Distance to Gas Station
  → Median of 2 sorted arrays
  → Kth element of 2 sorted arrays

Day 26–30: Strings

Things to do:

• Basic
  → Remove outermost Paranthesis
  → Reverse words in a given string/Palindrome Check
  → Largest odd number in a string
  → Longest Common Prefix
  → Isomorphic String
  → check whether one string is a rotation of another
  → Check if two strings are anagrams of each other

• Medium String Problem
  → Sort Characters by frequency
  → Maximum Nesting Depth of Paranthesis
  → Roman Number to Integer and vice versa
  → Implement Atoi
  → Count the Number of Substrings
  → Longest Palindromic Substring
  → Sum of Beauty of all substring
  → Reverse Every Word in A String

Day 31–41: LinkedList

Things to do:

• 1D LinkedList

• Doubly LinkedList

• Medium-Level Problems of LL
  → Middle of a LinkedList → Reverse a LinkedList
  → Detect if the linked list has a cycle in it
  → Find the starting point in LL
  → Length of Loop in LL
  → Check if LL is palindrome or not
  → Segregate odd and even nodes in LL
  → Remove the Nth node from the back of the LL
  → Delete the middle node of the LL
  → Sort LL
  → Sort a LL of 0’s and 1’s by changing links
  → Find the intersection point of Y LL
  → Add 1 to a number represented by LL
  → Add two numbers in LL

• Medium-Level Problems of DLL
  →Delete all occurrences of a key in DLL
  → Find pairs with given sum in DLL
  → Remove duplicates from sorted DLL

• Hard Level Problems of LL
  → Reverse LL in a group of given size K
  →Rotate a LL
  → Flattening of LL
  → Clone a LinkedList with random and next pointer

Day 42–62: Recursion

Things to do:

• Get a Strong Hold
  → Recursive Implementation of atoi()
  → Pow(x,n)
  → Count Good numbers
  → Sort a stack using recursion
  → Reverse a stack using recursion

• Subsequences Pattern
  → Generate all binary strings
  → Generate Parenthesis
  → Print all subsequences/Power Set
  → Learn All Patterns of Subsequences
  → Count all subsequences with sum K
  → Combination Sum
  → Combination Sum-II
  → Subset Sum-I
  → Subset Sum-II
  → Combination Sum — III
  → Letter Combinations of a Phone number

• Hard Level
  → Palindrome Partitioning
  → Word Search
  → N Queen
  → Rat in a Maze
  → Word Break
  → M Coloring Problem
  → Sudoku Solver
  → Expression Add Operators

Day 63–65: Bit Manipulation

Things to do:

• Basic
  → Introduction to Bit Manipulation
  → Check if the i-th bit is set or not
  → Check if a number is odd or not
  → Check if a number is a power of 2 or not
  → Count the number of set bits
  → Set/Unset the rightmost unset bit
  → Swap two numbers
  → Divide two integers without using multiplication, division and mod operator

• Interview Problems
  → Count the number of bits to be flipped to convert A to B
  → Find the number that appears an odd number of times
  → Power Set
  → Find xor of numbers from L to R
  → Find the two numbers appearing an odd number of times

• Advanced Maths
  → Print Prime Factors of a Number
  → All Divisors of a Number
  → Sieve of Eratosthenes
  → Find the Prime Factorization of a Number using Sieve
  → Power(n, x)

Day 65–75: Stack and Queues

Things to do:

• Learning
  → Implement Stacks using Arrays
  → Implement Queue using Arrays
  → Implement Stack using Queue
  → Implement Queue using Stack
  → Implement stacks using LinkedList
  → Implement Queue using LinkedList
  → Check for balanced parenthesis
  → Implement Min Stack

• Prefix, Infix, Postfix Conversion Problems
  → Infix to postfix Conversion using stack
  → Prefix to Infix Conversion
  → Prefix to Postfix Conversion
  → Postfix to Prefix Conversion
  → Postfix to Infix
  → Convert Infix to Prefix Notation

• **Monotonic Stack/Queue Problems
  → Next Greater Element
  → Next Greater Element 2
  → Next Smaller Element
  → Number of NGOs to the right
  → Trapping Rainwater
  → Sum of subarray minimum
  → Stock span problem
  → Asteroid Collision
  → Sum of subarray ranges
  → Remove k Digits
  → Largest rectangle in a histogram
  → Maximal Rectangles

• Implementation Problems
  → Sliding Window Maximum
  → Stock Span Problem
  → The Celebrity Problem → Rotten Oranges
  → LRU cache
  → LFU cache

Day 75–85: Greedy Algorithms

Things to do:

• Practice -link

Day 86–101: Binary Tree

Things to do:

• Basic
  → Basic tree structure
  → Traversing a Binary Tree (Preorder, Postorder, Inorder)
  → Balanced Binary Search Tree

• Problems
  → Find the height or depth of a binary tree
  → Finding the Diameter of a Tree using the height of each node
  →Find the number of Universal Value subtrees in a Binary Tree
  → Find if a given Binary Tree is a Sub-Tree of another Binary Tree
  → Finding nodes at a distance K from a given node
  → Copy a binary tree where each node has a random pointer
  → Zigzag Traversal of Binary Tree
  → Check if Binary Tree is foldable
  → Threaded Binary Tree
  → Convert Binary Tree to Threaded Binary Tree
  → Sum of k smallest elements in Binary Search Tree

Day 102–111: Graphs

Things to do:

• BFS/DFS

• Shortest path Algo

• Minimum spanning tree

• Union-Find

Refer: link

Day 112–120: Dynamic Programming

Things to do:

• Basic
  → link

• Problems
  → Climbing Stairs
  → Best Time to Buy and Sell Stock
  → Maximum Subarray
  → House Robber

• Hard Problems
  → Link

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