- The best way to prepare would be to clone this repo and mark the problems as completed as you progress along.
- If you're interested in explanations, check out DSA_Kotlin Repo, which has video explanations for every problem in this problem set.
- Arrays
- Trees
- Linked List
- Stack
- Queue
- Dynamic Programming
- Greedy Problems
- Divide and Conquer
- Bit Manipulation
- Mathematical
- Hashing
- String
- Pattern Matching
- Heaps
- Back Tracking
- Graphs
- One -> Linear Search
- Two -> Binary Search
- Three -> Find a pair in an array whose sum is equal to given number (Hash Approach) - Brute Force, Quick Sort and search complement, Hash Table
- Four -> Element that occurs more than n/2 times - Unsorted
- Five -> Element that occurs more than n/2 times - Sorted
- Six -> Largest Difference such that the smaller number appears before larger number
- Seven -> Largest Difference such that the smaller number appears before larger number - Less space complexity
- Eight -> Largest Difference such that the smaller number appears before larger number - Min So Far
- Nine -> Find the number occurring odd number of times in the given array(Only one element occurs odd number of times)
- Ten -> Separate 0's and 1's in an array
- Eleven -> Separate Even and Odd numbers in an array
- Twelve -> 2 elements whose sum is close to zero - either positive or negative
- Thirteen -> 3 elements such that their sum is equal to x.
- Fourteen -> Find the Equilibrium Index .i.e., left sum and right sum of index should be equal.
- Fifteen -> Find the Equilibrium Index .i.e., left sum and right sum of index should be equal - Less Space Complexity.
- Sixteen -> Array of unknown size. 0s followed by 1s find the first index of 1
- Seventeen -> Maximum of every contiguous sub-array of size k. - Sliding Window.
- Eighteen -> count the no.of smaller elements to the right of each element in the array.
- Nineteen -> Largest Multiple of 3 with given digits.
- Twenty -> Sub Array Sum equal to x
- TwentyOne -> Find Sub Array whose sum is equals zero
- TwentyTwo -> Largest sub array with equal no.of zeros and ones
- TwentyThree -> Construct a product array such that the ith element in product array contains the product of all the remaining elements but i (Without Division)
- TwentyFour -> Construct a product array such that the ith element in product array contains the product of all the remaining elements but i (Without Division) - less time complexity
- TwentyFive -> Sort a nearly sorted array, each element can be misplaced by a max of k digits before or after
- TwentySix -> Find Duplicates in O(n) time and O(1) space - Array element values are โค Max Index
- TwentySeven -> Find 2 repeating elements in a given array - XOR - Given (n+2) elements - 1 โค a[i] โค n - All elements from 1 to n occurs at least once (Except the 2 numbers that occurs twice)
- TwentyEight -> Rotate an array of size n by d elements - Left rotation - Beginning to End - Juggling Algorithm
- TwentyNine -> Sort array in wave form - Even position number
- Thirty -> Next least greater number to the given number, input as digit array - with same digits
- ThirtyOne -> Trapping Rain Water Problem
- ThirtyTwo -> No.of Triangles that can be formed
- ThirtyThree -> Smallest number that can't be formed from the array of given numbers
- ThirtyFour -> Rearrange such that a[i] becomes a[a[i]]
- ThirtyFive -> Rotate Matrix by 90 degree - anti-clockwise
- ThirtySix -> Count number of occurrences (or frequency) in a sorted array
- ThirtySeven -> Find Sub Array whose sum is equals zero - reduced time complexity
- ThirtyEight -> Largest sub array with equal no.of zeros and ones - my way
- One -> Size of a Binary Tree
- Two -> Identical or not
- Three -> Mirror Tree
- Four -> Level Order Traversal
- Five -> Lowest Common Ancestor (LCA) - BST
- Six -> Lowest Common Ancestor (LCA) - Binary Tree
- Seven -> Binary Tree into DLL - IN order - InPlace conversion
- Eight -> Diameter of the Binary Tree
- Nine -> Find the level of a given node
- Ten -> Print nodes at k distance form root
- Eleven -> Print nodes at K distance form any node in BT
- Twelve -> Vertical Tree Order Traversal
- Thirteen -> Vertical Sum of the Binary Tree
- Fourteen -> Sum Tree or not
- Fifteen -> Top View
- Sixteen -> Bottom View
- Seventeen -> Left View
- Eighteen -> Remove all paths whose length < K in BT.
- Nineteen -> One BT is a sub tree of another BT or not
- Twenty -> Cousin Nodes or not
- TwentyOne -> Balanced BST construction from a sorted List
- TwentyTwo -> BST into Balanced BST
- TwentyThree -> Print all paths possible from root to all leaves
- TwentyFour -> Spiral Level Order Traversal
- TwentyFive -> BT construction from the given POST and IN Order
- TwentySix -> All nodes at K distance from leaf
- TwentySeven -> Expression Evaluation
- TwentyEight -> Extreme nodes of each level in alternating order
- TwentyNine -> Diagonal Traversal BT
- Thirty -> BT to a BT that holds Child sum property
- ThirtyOne -> Multiplication of Sums of data of leaves at same level
- ThirtyTwo -> Multiplication of Sums of data at same level
- ThirtyThree -> Max of all differences of a node and it's ancestors BT
- ThirtyFour -> Serialization and Deserialization BT
- ThirtyFive -> Serialization and Deserialization n-ary Tree
- ThirtySix -> Tree from ancestor Matrix
- ThirtySeven -> Complete Binary Tree from a LL
- ThirtyEight -> Find the next right node of a given node in the same level
- ThirtyNine -> Boundary Traversal
- Forty -> Convert a given tree into sum tree
- FortyOne -> Check if Foldable or not
- FortyTwo -> Check if removing an edge will cut into two equal halves
- FortyThree -> Locking and Unlocking a Node - Design Problem
- FortyFour -> Reverse Alternate Levels of a perfect BT
- FortyFive -> Custom Tree Print Problem
- FortySix -> Threaded BT
- One -> Reverse a LL
- Two -> Middle of a LL
- Three -> Kth node from the end of the LL
- Four -> Detect loop in LL
- Five -> Find the start of the Loop in the LL with Loop
- Six -> 2 LL merge at a point, find that point
- Seven -> Alternating Split
- Eight -> Clone a LL that contains Random Pointer (Custom LL)
- Nine -> Palindrome of a LL
- Ten -> Merge 2 Sorted LL into one Sorted LL
- Eleven -> Merge K sorted LL of size N into single Sorted LL of size kn
- Twelve -> Merge sort on LL
- Thirteen -> LL with arb-pointer pointing to greatest in the right side of the current node
- Fourteen -> Memory efficient DLL
- Fifteen -> Sort a LL with 0s, 1s and 2s
- Sixteen -> Add 1 to number represented as LL
- Seventeen -> Merge K sorted LL of size N into single Sorted LL of size kn - Better complexity
- One -> Stack using Queues
- Two -> getMin @ O(1)
- Three -> Reverse a Stack
- Four -> closest greater element to the right
- Five -> Overlapping Intervals
- Six -> Balancing Parenthesis
- Seven -> Stock Span Problem
- Eight -> Min no.of bracket reversals req to make the eqn balanced
- Nine -> find duplicate parenthesis present or not
- Ten -> Celebrity Problem
- One -> Circular tour that visit all gasoline stations before running out of gas
- One -> Maximum Sum Sub array
- Two -> Maximum Sum Increasing Sub Sequence [OR] Longest increasing Sub Sequence
- Three -> Longest Sub Sequence in an array such that the element are consecutive
- Four -> In a Binary Matrix, Max Square Matrix with all 1s
- Five -> Kth Ugly Number
- Six -> Longest Increasing Sub Sequence
- Seven -> Longest Decreasing Sub Sequence
- Eight -> Perfect Hill Sequence
- Nine -> Edit Distance
- Ten -> Largest Sum Independent set in a Binary Tree
- Eleven -> Find n-bit integer that doesn't have 2 consecutive zeros
- Twelve -> Word breaking problem
- Thirteen -> Partition Problem - Sub Set Sum Problem
- Fourteen -> Longest Palindromic sub sequence
- Fifteen -> Steps 1 or 2 to reach n
- Sixteen -> Longest non overlapping repeating sub string
- Seventeen -> Min cost to make strings(x and y) equal, del(x) -> S, del(y) -> P
- Eighteen -> No.of times a string appeared as Sub Sequence in other string
- Nineteen -> No.of ways to fill 2xn with 2x1
- Twenty -> Given a Cost matrix, min cost to reach (m-1,n-1) from (0,0), allowed movements -> left, right, diagonally down
- TwentyOne -> K palindrome - If string becomes palindrome or not by doing atmost k deletions
- TwentyTwo -> Longest Common Sub Sequence
- TwentyThree -> Sum of all digits from 1 to n
- TwentyFour -> Given a string of digits, sub string length = 2k, sum of left k = sum of right k
- TwentyFive -> Given a BT, find Largest Independent Set
- TwentySix -> Cutting Rod
- TwentySeven -> Longest Palindromic sub string
- TwentyEight -> Count all Palindromic sub string in a string
- TwentyNine -> Count all distinct Palindromic sub string in a string
- Thirty -> Rectangular grid 2xn, max sum such that no 2 chosen digit are adj -> vertically, horizontally, diagonally
- ThirtyOne -> Arrays A -> m, B -> n, (m>n) insert(m-n) 0s in B such that dot product is max
- ThirtyTwo -> Largest Independent Set
- ThirtyThree -> Egg Dropping Problem
- ThirtyFour -> No.of Non-decreasing numbers with n digits
- ThirtyFive -> Weighted Job Scheduling
- ThirtySix -> Count no.of ways to reach a score in a given game, player can score 2, 4 or 6 points
- ThirtySeven -> Max coins by busting balloons
- ThirtyEight -> Max points in the grid using 2 traversals
- ThirtyNine -> Sub Set Sum Problem
- Forty -> Matrix Chaining - Results Upper triangular Matrix
- FortyOne -> Longest Common Sub Sequence
- FortyTwo -> Multi Stage Graph
- FortyThree -> 0/1 Knapsack
- FortyFour -> Travelling Sales man (TSP) - DFS based - Hamiltonian Cycle + MIN Cost
- FortyFive -> All Pair Shortest path - Floyd Warshall's
- FortySix -> Matrix Chaining - Top Down
- FortySeven -> Coin Change Problem
- FortyEight -> Longest Palindromic sub string - Less Space Complexity
- FortyNine -> No.of Non-decreasing numbers with n digits - Less space
- One -> n different ropes of different length, tie them up into a single rope with Min cost.
- Twp -> Maximum Non Overlapping Intervals
- Three -> Min no.of platforms required to station all trains without collision
- Four -> Rearrange the characters in the string such that same characters become d-distance away from each other.
- Five -> Dijkstra's Algorithm
- Six -> Fractional Knapsack
- Seven -> Huffman's Coding
- Eight -> Job Sequencing with Deadlines
- Nine -> Spanning Trees and kirchhoff's theorem
- Ten -> Minimum Spanning Tree - Prim's
- Eleven -> Kruskal's Algorithm
- Twelve -> Optimal Merge Patterns
- One -> Find the element that occurs more than n/2 times - Sorted Array.
- Two -> Bolt and Nuts
- Three -> Implement pow()
- Four -> Search an element in a sorted Rotated Array
- Five -> Count Inversions in an array
- Six -> Missing number in arithmetic progression
- Seven -> Array containing 0s before 1s, count 1s
- Eight -> Array has 2n elements ->
a1, a2, a3, .., an, b1, b2, .. , bn
-> shuffle ->a1, b1, a2, b2, .., an, bn
- Nine -> Sorted Array of non-repeating elements, find if there's
i
for whicha[i] = i
- Ten ->
a[0]..a[i]
-> increasing,a[i+1]..a[n]
-> decreasing, find i - Eleven -> search for an element in a row-wise and column-wise sorted 2d array.
- Twelve -> External Sorting
- Thirteen -> Find median of 2 sorted arrays
- Fourteen -> Find Peek Element
- Fifteen -> Get first 1.
- One -> Kth bit is set or not
- Two -> set Kth Bit of a number
- Three -> clear Kth bit of a number
- Four -> Toggle Kth bit of a number
- Five -> count the no.of set bits of a number
- Six -> power of 2 or not
- Seven -> next higher number of the given number which is a power of 2
- Eight -> power of 4 or not
- Nine -> Multiply with 7 without using
*
- Ten -> Check if a Number is Odd or Even using Bitwise Operators
- One -> Prime or not
- Two -> Print prime upto n - Sieve of Eratosthenes Algorithm
- Three -> Lucky number or not
- One -> check if the array has duplicate entries at K distance or not
- Two -> check if 2 sets are disjoint or not
- Three -> Group all occurrences of elements order by their 1st occurrence.
- Four -> Given an array A, count the distinct elements in all windows of size K
- Five -> Given an array and a range (low, high). Find the elements that are in the range but not in the array.
- Six -> Find the no.of sub arrays with sum zero
- Seven -> Find 4 elements i, j, k & l -> such that
i + j = k + l
- One -> Find a max occurring character in a given array.
- Two -> Remove duplicates in a given string
- Three -> Check if given 2 strings are rotations of each other
- Four -> Reverse the words in the given sentence
- Five -> Reverse a given string
- Six -> Check if palindrome
- Seven -> Find 1st non-repeating character in the given string
- Eight -> Run length encoding
- Nine -> Anagrams
- Ten -> Excel column name for a given excel column number (MS Excel)
- Eleven -> Find a smallest window in a string containing all characters of another string
- Twelve -> Find 1s non-repeating character in a stream of characters
- Thirteen -> All combinations of strings used to dail a number (Old Phone Key pad)
- Fourteen -> Min no.of palindromic sub-sequences to be removed to empty a binary string
- Fifteen -> Check if given sequence of moves for robot is circular or not
- Sixteen -> Min and Max of an array using min no.of comparisons
- Seventeen -> Convert one string to another using min no.of given operations
- Eighteen -> Print concatenation of zig-zack string in k-rows
- Nineteen -> Remove adj duplicate characters in a given string
- Twenty -> Min no.of palindromic sub-sequences to be removed to empty a binary string - Tournament Method
- One -> Find all occurrences of str2 in str1 - Brute force
- Two -> Knuth Morris Pratt Algorithm
- Three -> Boyer's Moore String Matching Algorithm
- Four -> Rabin-Karp String Matching Algorithm
- Five -> Find all occurrences of a given word in a matrix
- One -> Finding the max element in MIN heap
- Two -> Deleting arb element in MIN heap
- Three -> K-Largest elements from an array
- Four -> Median in a stream of numbers
- Five -> Given K-sorted list, find minimum range to which at least on number belongs from every list. - All list are of same size
- Six -> Convert MAX heap into MIN Heap
- Seven -> Print out all integers of the form
a^3+b^3
where a & b are integers b/w 0 & n in sorted order. - Eight -> Convert BST to MAX Heap
- Nine -> Find the Kth largest element in a stream
- Ten -> Tournament Tree
- Eleven -> Print all elements in sorted order in row wise and column wise sorted matrix
- Twelve -> Sort a nearly sorted array
- Thirteen -> Given n ropes with different length, connect with minimum cost.
- Fourteen -> Check if the given binary tree is a max heap or not.
- Fifteen -> Given K-sorted arrays of size n-each, merge them. - different sized inner lists
- Sixteen -> Delete root from a heap.
- One -> Print all permutations of given string
- Two -> Print all the strings of n-bits
- Three -> N-Queens Problem
- Four -> Rat in Maze
- Five -> Knight Tour Problem
- Six -> Find subset of elements that are selected from a given set whose sum adds upto a given number
k
// Subset Sum Problem - Using Backtracking - Seven -> SUDOKU
- Eight -> N-Queens Problem - Easy way
- One -> DFS
- Two -> BFS
- Three -> Find if there's a path between vi and vj in a directed graph
- Four -> Undirected Graph, cycle or not
- Five -> Bipartite or not
- Six -> Detect a cycle in a directed graph
- Seven -> Print all jumping numbers smaller than or equal to given value(k)
- Eight -> Single source shortest path - DAG
- Nine -> Longest Path in DAG, no weights
- Ten -> Find Articulation Point / Cut Vertex, Undirected
- Eleven -> Longest Path in DAG, with weights