Array
Question 1: Arrays: Find numbers with even number of digits
Question 2: Arrays: Find unique numbers that sum upto zero
Question 3: Arrays: Find the k’th smallest/largest element in an array
Question 4: Arrays: Check If N and Its Double Exist
Question 5: Arrays: Move all the negative number in beginning
Question 6: Arrays: Find the union and intersection of two sorted arrays
Question 7: Arrays: Given an array, rotate it one time
Question 9: Arrays: Minimize the maximum difference between the heights
Question 10: Arrays: Reach the end of the array with minimum jumps. Solution in C++
Question 11: Arrays: Given an array find the duplicate number
Question 12: Arrays: Merge Two Sorted arrays without using extra space
Question 13: Arrays: Kadane Algorithm
Question 14: Arrays: Merge overlapping Intervals solution in C++
Question 15: Arrays: Implement next permutation, which rearranges numbers into the next greater permutation of numbers.
Question 16: Arrays: Inversion Count in an Array
Question 17: Arrays: Optimum Time to Buy and Sell Stock
Question 19: Arrays: Find common element in 3 sorted arrays.
Question 20: Arrays: Rearrange the array with one positive and one negative number.
Question 21: Arrays: Given an array, find 3 elements such that [a + b + c] = 0. Find all the 3 unique elements.
Question 22: Arrays: Check if 3 consecutive odds exist
Question 23: Arrays: Given an integer array, find the maximum product made from continuous elements in that array.
Question 24: Arrays: Longest Increasing Subsequence
Question 25: Arrays: Given an array, find the majority element
Question 26: Arrays: Merge sorted array inplace
Question 27: Arrays: Find whether an array is subset of another array
Question 28: Arrays: Find a triplet that sum to a given value
Question 29: Arrays: Rain water trapping
Question 30: Arrays: Find triplet with minimum sum
Question 31: Arrays: Given an array of non repeating numbers and a key, find all the unique combinations in that array
Question 32: Arrays: Three way partitioning of an array around a given range
Question 33: Arrays: Minimum swaps required to bring all elements less than or equal to k together
Question 34: Arrays: Get minimum number of merge operations to make an array palindrome
Question 35: Arrays: Find the median of 2 sorted arrays of same size
Question 36: Arrays: Program to check if an Array is Palindrome or not
Question 37: Sort an array of 0s, 1s and 2s in C
Question 38: Given an array, the difference between the elements is one, find if the “key” element is present or not.
Matrix
Question 1: Matrix: Given a matrix of m x n elements , print all elements of the matrix in spiral order
Question 2: Matrix: Given a 2D Matrix and a key element, search and return if element is present or not
Question 3: Matrix: Find median in a row wise sorted matrix
Question 4: Matrix: Find a row with maximum number of 1’s in a binary matrix
Question 5: Matrix: Given a m x n matrix, if an element is 0, set its entire row and column to 0
Question 7: Matrix: Find pair with maximum sum in the matrix.
Question 8: Matrix: Given an n x n 2D matrix rotate it by 90 degrees
Question 9: Matrix: Kth smallest element in a sorted matrix
Question 1o: Matrix: Get the common elements in all row of a matrix.
Strings
Question 1: Strings: Reverse a string
Question 2: Strings: Remove all consecutive duplicates from the string
Question 3: Strings: Print all the duplicates in a string
Question 4: Strings: Given a string convert into its equivalent ASCII form
Question 5: Strings: Program to check if strings are rotations of each other or not
Question 6: Strings: Second most repeated word in a sequence
Question 7: Strings: Minimum Number of Swaps to Make the Binary String Alternating
Question 8: Strings: Given a string find the longest Palindromic Substring
Question 9: Strings: Longer Contiguous Segments of Ones than Zeros
Question 1o: Strings: Given a string, print all the subsequence
Question 11: Strings: Permutations of a given string
Question 12: Strings: Divide binary string into sub strings with equal number of 0s and 1s.
Question 13: Strings: Given a sentence and maxWidth. Arrange the text in such a way that each line has exactly maxWidth characters
Question 14: Strings: Min Edit Distance
Question 15: Strings: Longest Substring Of All Vowels in Order
Question 16: Strings: Check balanced parenthesis
Question 17: Strings: Check if it is possible to re-arrange characters in a string, such a way that no two adjacent are same
Question 18: Strings: Rabin Karp algorithm
Question 19: Strings: Knuth Morris Pratt String matching algorithm
Question 2o: Strings: Convert a string into its mobile numeric keypad
Question 21: Strings: Get the minimum number of inversions needed to make an expression balanced
Question 22: Strings: Given a string return all the substring that is a palindrome
Question 23: Strings: Count the number of string in 2D character array
Question 24: Strings: Given 2D matrix and a word, find if the word exists in the grid
Question 25: Strings: Boyer Moore algorithm
Question 26: Strings: Convert Roman Numerals to Decimal
Question 27: Strings: Longest Common Prefix
Question 28: Strings: Minimum number of flips to make binary string alternate
Question 29: Strings: Minimum swaps required for bracket balancing
Question 3o: Strings: Find the first repeated word in a string
Question 31: Strings: Find the longest common subsequence between two strings.
Question 32: Strings: Given a string of integers, restore all valid IP addresses
Question 33: Strings: Smallest distinct window
Question 34: Strings: Check if it is possible to re-arrange characters in a string, such a way that no two adjacent are same
Question 35: Strings: Check if Word Equals Summation of Two Words
Question 36: Strings: Group Anagrams
Question 37: Strings: Minimum Window Substring
Question 38: Strings: Remove all consecutive duplicates from the string
Question 39: Strings: Wildcard Matching
Question 4o: Strings: Longest Prefix Suffix
Question 41: Strings: Find minimum operations required to transform a string into another string
Question 42: Strings: Given 2 strings, check if they are isomorphic strings
Question 43: Strings: Recursively print all sentences that can be formed from list of word lists
Question 44: Strings: Number of Different Integers in a String
Searching & Sorting
Question 1: Searching & Sorting: Find the first and last occurrence of an element
Question 2: Searching and Sorting: Get the fixed point in an array
Question 5: Searching and Sorting: Maximum and minimum of an array using minimum number of comparisons
Question 6: Searching and Sorting: Binary search on an array that is in descending order
Question 7: Searching and Sorting: Order-Agnostic Binary Search
Question 8: Searching and Sorting: Find the majority element in the array
Question 9: Searching and Sorting: Search an array where adjacent differ by at most k
Question 1o: Searching and Sorting: Count all distinct pairs with difference equal to k
Question 12: Searching and Sorting: Maximum sum such that no two elements are adjacent
Question 14: Searching and Sorting: Merge 2 sorted arrays
Question 15: Searching and Sorting: print all subarrays with 0 sum
Question 16: Searching and Sorting: Product of array except itself
Question 17: Searching and Sorting: Sort Integers by The Number of 1 Bits
Question 18: Searching and Sorting: Minimum number of swaps required to sort an array
Question 19: Searching and Sorting: Find the smallest and second smallest elements in an array
Question 2o: Searching and Sorting: Find the number of times a Sorted array is Rotated
Question 21: Searching and Sorting: Searching in a Nearly Sorted Array
Question 22: Searching and Sorting: Find the minimum element from an array that is sorted and is rotated
Question 23: Searching and Sorting: K-th Element of Two Sorted Arrays
Question 24: Searching and Sorting: Find Floor of an element in a Sorted Array
Question 25: Searching and Sorting: Find Ceil of an element in a Sorted Array
Question 26: Searching and Sorting: Find position of an element in an Infinite Sorted Array
Question 27: Searching and Sorting: Job Sequencing with deadline Problem
Question 28: Searching and Sorting: Find the missing number in Arithmetic Progression
Question 29: Searching and Sorting: Factorial Trailing Zeroes
Question 3o: Searching and Sorting: Find the index of first 1 in an infinite sorted array of 0s and 1s
Question 31: Searching and Sorting: Peak Element
Question 32: Searching and Sorting: Find maximum element in Bitonic Array
Question 33: Searching and Sorting: Given a set of distinct integers, nums, return all possible subsets in CPP
Question 34: Searching and Sorting: Search An Element in Bitonic Array
Question 35: Searching and Sorting: Get the rotation count in sorted rotated array
Question 36: Searching and Sorting: Count the number of 1’s in an array sorted in decreasing order.
LinkedList
Question 1: Linked List: Reverse Linked List iterative and recursive
Question 2: Linked List: Reverse Linked List in groups
Question 3: Linked List: Given a linked list, check if it has a cycle in it, solution in C++
Question 4: Linked List: Rotate linked list by k nodes
Question 5: Linked List: Given a linked list, if it has a cycle, get the node where the cycle begins else return NULL.
Question 7: Linked List: Remove duplicates from an unsorted linked list
Question 8: Linked List: Move last element to front of a given Linked List
Question 9: Linked List: Add 1 to the linked list
Question 11: Linked List: Find Intersection of Two Linked Lists
Question 13: Linked List: Given an unsorted linked list, sort the list using merge sort
Question 14: Linked List: Reverse Linked List given 2 points m and n
Question 15: Linked List: Find middle element in Linked List
Question 16: Linked List: Perform below operations on Circular Singly Linked List
Question 17: Linked List: Split circular Linked List into two halves
Question 18: Linked List: Program to Check if a Singly Linked List is Palindrome
Question 19: Linked List: Deletion from a Circular Linked List
Question 2o: Linked List: Reverse a Doubly Linked List
Question 21: Linked List: Find pairs with a given sum in a DLL.
Question 22: Linked List: Count triplets in a sorted DLL whose sum is equal to given value “k”.
Question 23: Linked List: Sort a “k”sorted Doubly Linked list
Question 24: Linked List: Rotate Doubly linked list by N nodes
Question 25: Linked List: Rotate a Doubly Linked list in group of Given Size
Question 26: Linked List: Merge two sorted linked lists and return it as a new list
Question 27: Linked List: Given linked list swap Nodes in Pairs
Question 28: Linked List: Flatten a Linked List
Question 3o: Linked List: Merge k sorted linked lists and return it as one sorted list in C++
Question 31: Linked List: Multiply two numbers represented by Linked Lists
Question 32: Linked List: Delete nodes which have a greater value on right side using recursion
Question 33: Linked List: Segregate even and odd nodes in a Linked List
Question 34: Linked List: Given a linked list Remove Nth Node From End of List
Question 35: Linked List: Odd Even Linked List
Binary Trees
Question 1: Binary Trees: Level Order Traversal
Question 2: Binary Trees: Display Reverse Level Order Traversal by using queue
Question 3: Binary Trees: Height or Max depth of a BTree
Question 4: Binary Trees: Diameter of a Binary Tree
Question 5: Binary Trees: Convert a binary tree to its Mirror Tree
Question 6: Binary Trees: Perform InOrder traversal on a Binary Tree by without Recursion
Question 7: Binary Trees: Perform PreOrder traversal on a Binary Tree by without Recursion
Question 8: Binary Trees: Perform PostOrder traversal on a Binary Tree by without Recursion
Question 9: Binary Trees: Left view and right view of a Binary Tree
Question 1o: Binary Trees: Check if Binary Tree is Foldable Tree
Question 11: Binary Trees: Top view of a binary tree
Question 12: Binary Trees: Bottom view of binary Tree
Question 13: Binary Trees: Spiral order or Zigzag traversal of a Binary Tree
Question 14: Binary Trees: Check if binary tree is a height balanced tree?
Question 15: Binary Trees: Diagonal Traversal of a Binary tree
Question 16: Binary Trees: Boundary Traversal of Binary Tree
Question 17: Binary Trees: Get Maximum width of Binary Tree
Question 18: Binary Trees: Convert Binary Tree to DLL
Question 19: Binary Trees: Convert Binary tree into Sum tree
Question 2o: Binary Trees: Construct Binary Tree from preorder and inorder traversal
Question 21: Binary Trees: Minimum swap required to convert binary tree to binary search tree
Question 22: Binary Trees: Check if binary tree is a sum tree
Question 23: Binary Trees: Check if all Leaf Nodes are at same level in Binary tree
Question 24: Binary Trees: Find Duplicate Subtrees
Question 25: Binary Trees: Check if Two Trees are Mirror Structure to each other
Question 26: Binary Trees: Get Sum of all nodes formed from Root to Leaf Path
Question 27: Binary Trees: Check if a given graph is tree or not
Question 28: Binary Trees: Find largest subtree sum in a tree
Question 29: Binary Trees: Maximum Sum of nodes in Binary tree such that no two are adjacent
Question 3o: Binary Trees: Print all the paths from root node to leaf node
Question 31: Binary Trees: Lowest Common ancestor of a Binary Tree.
Question 32: Binary Trees: Print the nodes at k distance from the root of a binary tree
Question 33: Binary Trees: Kth Ancestor of a Tree Node
Question 34: Binary Trees: Find Duplicate Subtrees
Question 35: Binary Trees: Check if two Binary Trees are Isomorphic
Binary Search Trees
Question 1: Binary Search Trees: Find a value in a BST
Question 2: Binary Search Trees: Deletion of a node in a BST
Question 3: Binary Search Trees: Find min and max value in a BST
Question 4: Binary Search Trees: Find the Inorder predecessor and successor for a given key in BST
Question 5: Binary Search Trees: A program to check if a binary tree is BST or not
Question 6: Binary Search Trees: Convert a BST into greater sum tree
Question 7: Binary Search Trees: LCA in a BST
Question 8: Binary Search Trees: Construct BST from preorder traversal
Question 9: Binary Search Trees: Convert Binary Tree into Binary Search Tree.
Question 1o: Binary Search Trees: Convert a normal BST into a Balanced BST
Question 11: Binary Search Trees: Merge Two balanced BST
Question 12: Binary Search Trees: Kth Largest Element in a BST
Question 13: Binary Search Trees: Kth smallest Element in a BST
Question 14: Binary Search Trees: Return the sum of given range in BST.
Question 15: Binary Search Trees: Get the Shortest distance between two nodes in BST
Question 16: Binary Search Trees: Count the number of BST nodes that lie in a given range.
Question 17: Binary Search Trees: Convert sorted DLL to Balanced BST
Question 18: Binary Search Trees: Find triplet sum in BST
Question 19: Binary Search Trees: Check if the pre-order is a valid BST
Question 2o: Binary Search Trees: Check if the BST has a dead end
Question 21: Binary Search Trees: Correct a BST where 2 nodes are swapped
Question 22: Binary Search Trees: Flatten BST to sorted list
Greedy
Question 1: Greedy: Activity Selection Problem
Question 2: Greedy: Job Sequencing with deadline Problem
Question 3: Greedy: Remove duplicates from a string
Question 4: Greedy: Add elements in an array so the sum is equal to the given range
Question 5: Greedy: Fractional knapsack tutorial with implementation
Question 6:
Question 7: Greedy: Remove k digits from an number to make it a smallest integer.
Question 8: Greedy: Get the minimum platforms needed to avoid delay in the train arrival.
Question 9: Greedy: Check if the string is a substring of another string
Question 1o: Greedy: Remove overlapping intervals.
Question 11: Greedy: Plant n flowers in flower bed
Question 12: Greedy: Maximum meetings in one room
Question 13: Greedy: Distribute Candy
Question 14: Greedy: Shuffle array so that one array element is greater than other array element
Question 15: Greedy: Schedule task efficiently
Question 16: Greedy: Partition characters
Question 17: Greedy: Maximum sum of absolute difference of an array
Question 18: Greedy: Juice change
Question 19: Greedy: Given a string, split into balanced strings.
Question 2o: Greedy: Perform operations on a broker calculator
Question 21: Greedy: Add minimum to make parentheses valid.
Question 22: Greedy: Remove covered intervals.
Question 23:
Question 24: Greedy: Reduce the array size to the half
Question 25: Greedy: Connect ropes with minimum cost.
Question 26: Dijkstra’s Algorithm
Question 27:
Question 28: Kruskal’s algorithm
Question 29: Greedy: Connect ropes with minimum cost.
Question 3o:
Question 31:
Question 32: Greedy: Find maximum sum possible equal sum of three stacks
BackTracking
Question 1: Backtracking: Partition string into its palindrome
Question 2: Backtracking: Letter Combinations of a Phone Number
Question 3: Backtracking: Solve Sudoku
Question 4: Backtracking: Check if the given board is valid Sudoku or not
Question 5: Backtracking: N-Queens
Question 9: Backtracking: Get the k combination from an array of 1 to n
Question 1o: Backtracking: Given array of integers that might contain duplicates, return all the subsets
Question 11: Backtracking: Find combination sum of k numbers that sum up to n
Question 13: Backtracking: Letter case permutation
Question 14: Backtracking: Return the number of queens possible in a chessboard
Question 15: Backtracking: Get the sequential digits from the given range
Question 16: Backtracking: Partition to K Equal Sum Subsets
Question 17: Backtracking: Get maximum sum in a matrix
Brute Force:
HashMap Technique:
Top-Down and/or Bottom Up approach
Question 1: Count the number of ways a baby can reach the nth stair taking 1 or 2 steps at a time in C language.