Step 1 : Learn the basics

Step 1.1 : Things to Know in C++/Java/Python or any language

	Topic/Article	GfG	Solution	Leetcode
	User Input / Output
	Data Types
	If Else statements
	Switch Statement
	What are arrays, strings?
	For loops
	While loops
	Functions (Pass by Reference and Value)
	Time Complexity [Learn Basics, and then analyse in next Steps]

Step 1.2 : Build-up Logical Thinking

• Do all these patterns

	Topic/Article	Solution
	Patterns

Step 1.3 : Learn STL/Java-Collections or similar thing in your language

	Topic/Article	Solution
	Java Collections or C++ STL

Step 1.4 : Know Basic Maths

	Topic/Article	GfG	Solution	Leetcode
	Count Digits
	Reverse a Number
	Check Palindrome
	GCD Or HCF
	Armstrong Numbers
	Print all Divisors
	Check for Prime

Step 1.5 : Learn Basic Recursion

	Topic/Article	GfG	Solution	Leetcode
	Understand recursion by print 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 palindrome or not
	Fibonacci Number

Step 1.6 : Learn Basic Hashing

	Topic/Article	GfG	Solution	Leetcode
	Hashing Theory
	Counting frequencies of array elements
	Find the highest/lowest frequency element

Step 2 : Learn Important Sorting Techniques

Step 2.1 : Sorting-I

	Topic/Article	GfG	Video	Leetcode
	Selection Sort
	Bubble Sort
	Insertion Sort

Step 2.2 : Sorting-II

	Topic/Article	GfG	Video	Leetcode
	Merge Sort
	Recursive Bubble Sort
	Recursive Insertion Sort
	Quick Sort

Step 3 : Solve Problems on Arrays [Easy ->Medium ->Hard]

Step 3.1 : Easy

	Topic/Article	GfG	Solution	Leetcode
	Largest Element in an Array
	Second Largest Element in an Array without sorting
	Check if the array is sorted
	Remove duplicates from Sorted array
	Left Rotate an array by one place
	Left rotate an array by D places
	Move Zeros to end
	Linear Search
	Find the Union and intersection of two sorted arrays
	Find missing number in an array
	Maximum Consecutive Ones
	Find the number that appears once, and other numbers twice.
	Longest subarray with given sum(Positives)
	Longest subarray with given sum(Positives + Negatives)

Step 3.2 : Medium

	Topic/Article	GfG	Solution	Leetcode
	2Sum Problem
	Sort an array of 0 ’s 1 ’s and 2 ’s
	Majority Element (>n/2 times)
	Kadane ’s Algorithm, maximum subarray sum
	Print the subarray with maximum sum
	Stock Buy and Sell
	Rearrange the array in alternating positive and negative items
	Next Permutation
	Leaders in an Array problem
	Longest Consecutive Sequence in an Array
	Set Matrix Zeros
	Rotate Matrix by 90 degrees
	Print the matrix in spiral manner
	Find number of subarrays with sum K

Step 3.3 : Hard

	Topic/Article	GfG	Solution	Leetcode
	Pascal ’s Triangle
	Majority Element (n/3 times)
	3-Sum Problem
	4-Sum Problem
	Count number of subarrays with given xor K
	Merge Overlapping Subintervals
	Merge two sorted arrays without extra space
	Find the repeating and missing number
	Count Inversions
	Reverse Pairs
	Maximum Product Subarray

Step 4 : Binary Search [1D, 2D Arrays, Search Space]

Step 4.1 : Learning BS on 1D Arrays

	Topic/Article	GfG	Solution	Leetcode
	Binary Search to find X in sorted array
	Implement Lower Bound
	Implement Upper Bound
	Search Insert Position
	Floor/Ceil in Sorted Array
	Find the first or last occurrence of a given number in a sorted array
	Count occurrences 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
	Find out how many times has an array been rotated
	Single element in a Sorted Array

Step 4.2 : Applying BS on 2D Arrays

	Topic/Article	GfG	Solution	Leetcode
	Find the row with maximum number of 1 ’s
	Search in a 2 D matrix
	Find Peak Element
	Matrix Median

Step 4.3 : Find Answers by BS in Search Space

	Topic/Article	GfG	Solution	Leetcode
	Find square root of a number in log n
	Find the Nth root of a number using binary search
	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

Step 5 : Strings [Basic and Medium]

• String has extremely hard problems for beginners in its hard section, so it is covered in the later half
• String has lesser problems, because most of the string problems have hard concepts like DP or others which are covered in different topics.

Step 5.1 : Basic and Easy String Problems

	Topic/Article	GfG	Solution	Leetcode
	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 anagram of each other

Step 5.2 : Medium String Problems

	Topic/Article	GfG	Solution	Leetcode
	Sort Characters by frequency
	Maximum Nesting Depth of Paranthesis
	Roman Number to Integer and vice versa
	Implement Atoi
	Count Number of Substrings
	Longest Palindromic Substring[Do it without DP]
	Sum of Beauty of all substring
	Reverse Every Word in A String

Step 6 : Learn LinkedList [Single/Double LL, Medium, Hard]

Step 6.1 : Learn 1D LinkedLis

	Topic/Article	GfG	Solution	Leetcode
	Introduction to LinkedList, learn about struct, and how is node represented
	Inserting a node in LinkedList
	Deleting a node in LinkedList
	Find the length of the linkedlist [learn traversal]
	Search an element in the LL

Step 6.2 : Learn Doubly LinkedLis

	Topic/Article	GfG	Solution	Leetcode
	Introduction to DLL, learn about struct, and how is node represented
	Insert a node in DLL
	Delete a node in DLL
	Reverse a DLL

Step 6.3 : Medium Problems of LL

	Topic/Article	GfG	Solution	Leetcode
	Middle of a LinkedList [TortoiseHare Method]
	Reverse a LinkedList [Iterative]
	Reverse a LL [Recursive]
	Detect a loop in LL
	Find the starting point in LL
	Length of Loop in LL
	Check if LL is palindrome or not
	Segrregate odd and even nodes in LL
	Remove Nth node from the back of the LL
	Delete the middle node of LL
	Sort LL
	Sort a LL of 0 ’s 1 ’s and 2 ’s by changing links
	Find the intersection point of Y LL
	Add 1 to a number represented by LL
	Add 2 numbers in LL

Step 6.4 : Medium Problems of DLL

	Topic/Article	GfG	Solution	Leetcode
	Delete all occurrences of a key in DLL
	Find pairs with given sum in DLL
	Remove duplicates from sorted DLL

Step 6.5 : Hard Problems of LL

	Topic/Article	GfG	Solution	Leetcode
	Reverse LL in group of given size K
	Rotate a LL
	Flattening of LL
	Clone a Linked List with random and next pointer

Step 7 : Recursion [PatternWise]

• Please complete the basic recursion questions in Step 1
• To learn completely recursion, watch this playlist ->Link

Step 7.1 : Get a Strong Hold

	Topic/Article	GfG	Solution	Leetcode
	Recursive Implementation of atoi()
	Pow(x, n)
	Count Good numbers
	Sort a stack using recursion
	Reverse a stack using recursion

Step 7.2 : Subsequences Pattern

	Topic/Article	GfG	Solution	Leetcode
	Generate all binary strings
	Generate Paranthesis
	Print all subsequences/Power Set
	Learn All Patterns of Subsequences (Theory)
	Count all subsequences with sum K
	Check if there exists a subsequence with sum K
	Combination Sum
	Combination Sum-II
	Subset Sum-I
	Subset Sum-II
	Combination Sum –III
	Letter Combinations of a Phone number

Step 7.3 : Trying out all Combos / Hard

	Topic/Article	GfG	Solution	Leetcode
	Palindrome Partitioning
	Word Search
	N Queen
	Rat in a Maze
	Word Break
	M Coloring Problem
	Sudoko Solver
	Expression Add Operators

Step 8 : Bit Manipulation [Concepts &Problems] &Advanced Maths

• It is one of the smallest topics in DSA, learn the basic concepts.
• There are only few problems which are repeatedly asked in Interviews which have been added.

Step 8.1 : Learn Bit Manipulation

	Topic/Article	GfG	Solution	Leetcode
	Introduction to Bit Manipulation [Theory]
	Check if the i-th bit is set or not
	Check if a number is odd or not
	Check if a number is 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

Step 8.2 : Interview Problems

	Topic/Article	GfG	Solution	Leetcode
	Count number of bits to be flipped to convert A to B
	Find the number that appears odd number of times
	Power Set
	Fnd xor of numbers from L to R
	Find the two numbers appearing odd number of times

Step 8.3 : Advanced Maths

	Topic/Article	GfG	Solution	Leetcode
	Print Prime Factors of a Number
	All Divisors of a Number
	Sieve of Eratosthenes
	Find Prime Factorisation of a Number using Sieve
	Power(n, x)

Step 9 : Stack and Queues [Pre-In-Post-fix, Monotonic Stack]

Step 9.1 : Learning

	Topic/Article	GfG	Solution	Leetcode
	Implement Stack using Arrays
	Implement Queue using Arrays
	Implement Stack using Queue
	Implement Queue using Stack
	Implement stack using Linkedlist
	Implement queue using Linkedlist
	Check for balanced paranthesis
	Implement Min Stack

Step 9.2 : Prefix, Infix, PostFix Conversion Problems

	Topic/Article	GfG	Solution	Leetcode
	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

Step 9.3 : Monotonic Stack/Queue Problems [VVV. Imp]

	Topic/Article	GfG	Solution	Leetcode
	Next Greater Element
	Next Greater Element 2
	Next Smaller Element
	Number of NGEs 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

Step 9.4 : Implementation Problems

	Topic/Article	GfG	Solution	Leetcode
	Sliding Window maximum
	Stock Span Problem
	The Celebrity Problem
	Rotten Oranges
	LRU cache (IMPORTANT)
	LFU cache

Step 10 : Sliding Window &Two Pointer Combined Problems

Step 10.1 : Medium Problems

	Topic/Article	GfG	Solution	Leetcode
	Longest Substring Without Repeating Characters
	Max Consecutive Ones III
	Fruit Into Baskets
	longest repeating character replacement
	Binary subarray with sum
	Count number of nice subarrays
	Number of substring containing all three characters
	Maximum point you can obtain from cards

Step 10.2 : Hard Problems

	Topic/Article	GfG	Solution	Leetcode
	Longest Substring with At Most K Distinct Characters
	Subarray with k different integers
	Minimum Window Substring
	Minimum Window Subsequence			Problem 2

Step 11 : Heaps [Learning, Medium, Hard Problems]

Step 11.1 : Learning

	Topic/Article	GfG	Solution	Leetcode
	Introduction to Priority Queues using Binary Heaps
	Min Heap and Max Heap Implementation
	Check if an array represents a min-heap or not
	Convert min Heap to max Heap

Step 11.2 : Medium Problems

	Topic/Article	GfG	Solution	Leetcode
	Kth largest element in an array [use priority queue]
	Kth smallest element in an array [use priority queue]
	Sort K sorted array
	Merge M sorted Lists
	Replace each array element by its corresponding rank
	Task Scheduler
	Hands of Straights

Step 11.3 : Hard Problems

	Topic/Article	GfG	Solution	Leetcode
	Design twitter
	Connect `n` ropes with minimal cost
	Kth largest element in a stream of running integers
	Maximum Sum Combination
	Find Median from Data Stream
	K most frequent elements

Step 12 : Greedy Algorithms [Easy, Medium/Hard]

Step 12.1 : Easy Problems

	Topic/Article	GfG	Solution	Leetcode
	Assign Cookies
	Fractional Knapsack Problem
	Greedy algorithm to find minimum number of coins
	Lemonade Change
	Valid Paranthesis Checker

Step 12.2 : Medium/Hard

	Topic/Article	GfG	Solution	Leetcode
	N meetings in one room
	Jump Game
	Jump Game 2
	Minimum number of platforms required for a railway
	Job sequencing Problem
	Candy
	Program for Shortest Job First (or SJF) CPU Scheduling
	Program for Least Recently Used (LRU) Page Replacement Algorithm
	Insert Interval
	Merge Intervals
	Non-overlapping Intervals

Step 13 : Binary Trees [Traversals, Medium and Hard Problems]

• An entire playlist is made on it, it is more than enough

Step 13.1 : Traversals

	Topic/Article	GfG	Solution	Leetcode
	Introduction to Trees
	Binary Tree Representation in C++
	Binary Tree Representation in Java
	Binary Tree Traversals in Binary Tree
	Preorder Traversal of Binary Tree
	Inorder Traversal of Binary Tree
	Post-order Traversal of Binary Tree
	Level order Traversal / Level order traversal in spiral form
	Iterative Preorder Traversal of Binary Tree
	Iterative Inorder Traversal of Binary Tree
	Post-order Traversal of Binary Tree using 2 stack
	Post-order Traversal of Binary Tree using 1 stack
	Preorder, Inorder, and Postorder Traversal in one Traversal

Step 13.2 : Medium Problems

	Topic/Article	GfG	Solution	Leetcode
	Height of a Binary Tree
	Check if the Binary tree is height-balanced or not
	Diameter of Binary Tree
	Maximum path sum
	Check if two trees are identical or not
	Zig Zag Traversal of Binary Tree
	Boundary Traversal of Binary Tree
	Vertical Order Traversal of Binary Tree
	Top View of Binary Tree
	Bottom View of Binary Tree
	Right/Left View of Binary Tree
	Symmetric Binary Tree

Step 13.1 : Hard Problems

	Topic/Article	GfG	Solution	Leetcode
	Root to Node Path in Binary Tree
	LCA in Binary Tree
	Maximum width of a Binary Tree
	Check for Children Sum Property
	Print all the Nodes at a distance of K in a Binary Tree
	Minimum time taken to BURN the Binary Tree from a Node
	Count total Nodes in a COMPLETE Binary Tree
	Requirements needed to construct a Unique Binary Tree | Theory			Link
	Construct Binary Tree from inorder and preorder
	Construct the Binary Tree from Postorder and Inorder Traversal
	Serialize and deserialize Binary Tree
	Morris Preorder Traversal of a Binary Tree
	Morris Inorder Traversal of a Binary Tree
	Flatten Binary Tree to LinkedList

Step 14 : Binary Search Trees [Concept and Problems]

• An entire playlist is made on it, it is more than enough

Step 14.1 : Concepts

	Topic/Article	GfG	Solution	Leetcode
	Introduction to Binary Search Tree
	Search in a Binary Search Tree
	Find Min/Max in BST

Step 14.2 : Practice Problems

	Topic/Article	GfG	Solution	Leetcode
	Ceil in a Binary Search Tree
	Floor in a Binary Search Tree
	Insert a given Node in Binary Search Tree
	Delete a Node in Binary Search Tree
	Find K-th smallest/largest element in BST
	Check if a tree is a BST or BT
	LCA in Binary Search Tree
	Construct a BST from a preorder traversal
	Inorder Successor/Predecessor in BST
	Merge 2 BST ’s
	Two Sum In BST | Check if there exists a pair with Sum K
	Recover BST | Correct BST with two nodes swapped
	Largest BST in Binary Tree

Step 15 : Graphs [Concepts &Problems]

• The new Graph playlist is under progress, you can check here ->Link
• In case you have lesser time, you can check the old graph series here ->Link

Step 15.1 : Learning

	Topic/Article	GfG	Solution	Leetcode
	Graph and Types
	Graph Representation | C++
	Graph Representation | Java
	Connected Components | Logic Explanation
	BFS
	DFS

Step 15.2 : Problems on BFS/DFS

	Topic/Article	GfG	Solution	Leetcode
	Number of provinces (leetcode)
	Connected Components Problem in Matrix
	Rotten Oranges
	Flood fill
	Cycle Detection in unirected Graph (bfs)
	Cycle Detection in undirected Graph (dfs)
	0/1 Matrix (Bfs Problem)
	Surrounded Regions (dfs)
	Number of Enclaves [flood fill implementation –multisource]
	Word ladder –1
	Word ladder –2
	Number of Distinct Islands [dfs multisource]
	Bipartite Graph (DFS)
	Cycle Detection in Directed Graph (DFS)

Step 15.3 : Topo Sort and Problems

	Topic/Article	GfG	Solution	Leetcode
	Topo Sort
	Kahn ’s Algorithm
	Cycle Detection in Directed Graph (BFS)
	Course Schedule –I
	Course Schedule –II
	Find eventual safe states
	Alien dictionary

Step 15.4 : Shortest Path Algorithms and Problems

	Topic/Article	GfG	Solution	Leetcode
	Shortest Path in UG with unit weights
	Shortest Path in DAG
	Djisktra ’s Algorithm
	Why priority Queue is used in Djisktra ’s Algorithm
	Shortest path in a binary maze
	Path with minimum effort
	Cheapest flights within k stops
	Network Delay time
	Number of ways to arrive at destination
	Minimum steps to reach end from start by performing multiplication and mod operations with array elements
	Bellman Ford Algorithm
	Floyd Warshal Algorithm
	Find the city with the smallest number of neighbors in a threshold distance

Step 15.5 : MinimumSpanningTree/Disjoint Set and Problems

	Topic/Article	GfG	Solution	Leetcode
	Minimum Spanning Tree
	Prim ’s Algorithm
	Disjoint Set [Union by Rank]
	Disjoint Set [Union by Size]
	Kruskal ’s Algorithm
	Number of operations to make network connected
	Most stones removed with same rows or columns
	Accounts merge
	Number of island II
	Making a Large Island
	Swim in rising water			[HARD]

Step 15.6 : Other Algorithms

	Topic/Article	GfG	Solution	Leetcode
	Bridges in Graph
	Articulation Point
	Kosaraju ’s Algorithm

Step 16 : Dynamic Programming [Patterns and Problems]

• An entire playlist is made on it, it is more than enough

Step 16.1 : Introduction to DP

	Topic/Article	GfG	Solution	Leetcode
	Dynamic Programming Introduction

Step 16.2 : 1D DP

	Topic/Article	GfG	Solution	Leetcode
	Climbing Stars
	Frog Jump(DP-3)
	Frog Jump with k distances(DP-4)
	Maximum sum of non-adjacent elements (DP 5)
	House Robber (DP 6)

Step 16.3 : 2D/3D DP and DP on Grids

	Topic/Article	GfG	Solution	Leetcode
	Ninja’s Training (DP 7)
	Grid Unique Paths : DP on Grids (DP8)
	Grid Unique Paths 2 (DP 9)
	Minimum path sum in Grid (DP 10)
	Minimum path sum in Triangular Grid (DP 11)
	Minimum/Maximum Falling Path Sum (DP-12)
	3-d DP : Ninja and his friends (DP-13)

Step 16.4 : DP on Subsequences

	Topic/Article	GfG	Solution	Leetcode
	Subset sum equal to target (DP- 14)
	Partition Equal Subset Sum (DP- 15)
	Partition Set Into 2 Subsets With Min Absolute Sum Diff (DP- 16)
	Count Subsets with Sum K (DP – 17)
	Count Partitions with Given Difference (DP – 18)
	0/1 Knapsack (DP – 19)
	Minimum Coins (DP – 20)
	Target Sum (DP – 21)
	Coin Change 2 (DP – 22)
	Unbounded Knapsack (DP – 23)
	Rod Cutting Problem | (DP – 24)

Step 16.5 : DP on Strings

	Topic/Article	GfG	Solution	Leetcode
	Longest Common Subsequence | (DP – 25)
	Print Longest Common Subsequence | (DP – 26)
	Longest Common Substring | (DP – 27)
	Longest Palindromic Subsequence | (DP-28)
	Minimum insertions to make string palindrome | DP-29
	Minimum Insertions/Deletions to Convert String | (DP- 30)
	Shortest Common Supersequence | (DP – 31)
	Distinct Subsequences| (DP-32)
	Edit Distance | (DP-33)
	Wildcard Matching | (DP-34)

Step 16.6 : DP on Stocks

	Topic/Article	GfG	Solution	Leetcode
	Best Time to Buy and Sell Stock |(DP-35)
	Buy and Sell Stock – II|(DP-36)
	Buy and Sell Stocks III|(DP-37)
	Buy and Stock Sell IV |(DP-38)
	Buy and Sell Stocks With Cooldown|(DP-39)
	Buy and Sell Stocks With Transaction Fee|(DP-40)

Step 16.7 : DP on LIS

	Topic/Article	GfG	Solution	Leetcode
	Longest Increasing Subsequence |(DP-41)
	Printing Longest Increasing Subsequence|(DP-42)
	Longest Increasing Subsequence |(DP-43)
	Largest Divisible Subset|(DP-44)
	Longest String Chain|(DP-45)
	Longest Bitonic Subsequence |(DP-46)
	Number of Longest Increasing Subsequences|(DP-47)

Step 16.8 : MCM DP | Partition DP

	Topic/Article	GfG	Solution	Leetcode
	Matrix Chain Multiplication|(DP-48)
	Matrix Chain Multiplication | Bottom-Up|(DP-49)
	Minimum Cost to Cut the Stick|(DP-50)
	Burst Balloons|(DP-51)
	Evaluate Boolean Expression to True|(DP-52)
	Palindrome Partitioning – II|(DP-53)
	Partition Array for Maximum Sum|(DP-54)

Step 16.9 : DP on Squares

	Topic/Article	GfG	Solution	Leetcode
	Maximum Rectangle Area with all 1’s|(DP-55)
	Count Square Submatrices with All Ones|(DP-56)

Step 17 : Tries [Concepts and Problems]

• Trie has limited problems, and usually they ask directly.
• An entire playlist is made on it, you don ’t need anything out of what is given below.

Step 17.1 : Theory

	Topic/Article	GfG	Solution	Leetcode
	Implement TRIE | INSERT | SEARCH | STARTSWITH

Step 17.2 : Problems

	Topic/Article	GfG	Solution	Leetcode
	Implement Trie – 2 (Prefix Tree)
	Longest String with All Prefixes
	Number of Distinct Substrings in a String
	Bit PreRequisites for TRIE Problems
	Maximum XOR of two numbers in an array
	Maximum XOR With an Element From Array

Step 18 : Strings [Hard Problems and Standard Algos]

• Basic, Medium, and other concepts on Strings have been covered above.
• In this we cover the algorithms, and applications which are generally asked, it is slightly tough to understand intuition wise, so don ’t be much concerned.

Step 18.1 : Hard Problems

	Topic/Article	GfG	Solution	Leetcode
	Minimum number of bracket reversals needed to make an expression balanced
	Count and say
	Hashing In Strings | Theory
	Rabin Karp
	Z-Function
	KMP algo / LPS(pi) array
	Shortest Palindrome
	Longest happy prefix
	Count palindromic subsequence in given string