Top Coding DSA Questions for Placements 2024

Welcome to our comprehensive resource guide for mastering Data Structures and Algorithms (DSA)! Whether you're a beginner or an experienced developer, this blog is designed to help you improve your coding skills and crack tough interviews.

In this resource guide, we've curated a list of essential DSA problems, including:

• Dynamic Programming

• Binary Search

• Array and Matrix problems

• Graph and Tree problems

• Backtracking and Miscellaneous problems

Each problem comes with a detailed explanation, approach, and solution to help you understand the concepts and implement them efficiently.

What to Expect:

• Expert-curated problems and solutions

• Step-by-step explanations and approaches

• Code snippets in popular programming languages

• Regular updates with new problems and solutions

• Interview-specific questions and tips

Who is this guide for?

• Beginners looking to build a strong foundation in DSA

• Experienced developers seeking to improve their coding skills

• Interview candidates preparing for technical interviews

• Coding enthusiasts who want to stay up-to-date with the latest DSA trends

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The Questions given below are from the students who are placed for the year 2024:

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Dynamic Programming:

1. DP Stock Question:

   Problem Statement: Given an array of stock prices, find the maximum profit that can be achieved by buying and selling stocks.

   Approach: Use dynamic programming to track the maximum profit at each step. Initialize two variables: buy and sell. Iterate through the array, updating buy and sell based on whether it's better to buy or sell at each step.

2. Good Subarray:

   Problem Statement: Find the number of good subarrays in an array, where a good subarray is defined as one with a sum equal to 0.

   Approach: Use a hashmap to store the cumulative sum of elements. Iterate through the array, updating the cumulative sum and checking if it exists in the hashmap.

3. LinkedList Intersection:

   Problem Statement: Find the intersection point of two linked lists.

   Approach: Use two pointers to traverse both linked lists. Calculate the difference in lengths and move the pointer of the longer list accordingly.

4. Fibonacci Series:

   Problem Statement: Find the nth Fibonacci number using dynamic programming.

   Approach: Create an array to store Fibonacci numbers. Initialize the first two elements and iterate through the array, updating each element as the sum of the previous two.

5. Subsequence Question:

   Problem Statement: Find the longest common subsequence between two strings.

   Approach: Create a 2D array to store lengths of common subsequences. Iterate through both strings, updating the array based on matches.

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Binary Search:

1. Twisted Binary Search:

   Problem Statement: Find an element in a twisted sorted array.

   Approach: Modify the standard binary search algorithm to account for the twist.

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Array:

1. Good Subarrays with Sum as 0:

   Problem Statement: Find the number of good subarrays with a sum equal to 0.

   Approach: Use a hashmap to store the cumulative sum of elements.

2. 2D Array Sum:

   Problem Statement: Find the maximum sum of a subarray in a 2D array.

   Approach: Use Kadane's algorithm to find the maximum sum of subarrays in each row and column.

3. Second Largest Element:

   Problem Statement: Find the second largest element in an array.

   Approach: Iterate through the array, keeping track of the maximum and second maximum elements.

4. Kth Largest Element:

   Problem Statement: Find the kth largest element in an array.

   Approach: Use a priority queue or quickselect algorithm.

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Matrix Problems:

1. Spiral Matrix Traversal:

   Problem Statement: Traverse a matrix in a spiral order.

   Approach: Use four pointers to keep track of the current boundaries.

2. Diagonal Traversal of a 2D Matrix:

   Problem Statement: Traverse a matrix diagonally.

   Approach: Use two pointers to keep track of the current diagonal

3. Reverse a String without Changing Special Characters:

   Problem Statement: Reverse a string without changing the positions of special characters.

   Approach: Use two pointers to swap characters.

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Graph Problems:

1. Find Shortest Path between Two Nodes in a Binary Tree:

   Problem Statement: Find the shortest path between two nodes in a binary tree.

   Approach: Use DFS or BFS to find the lowest common ancestor.

2. Find Second Largest Element in an Array without Sorting:

   Problem Statement: Find the second largest element in an array without sorting.

   Approach: Iterate through the array, keeping track of the maximum and second maximum elements.

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BackTracking:

1. Hanoi's Tower:

   Problem Statement: Move a stack of disks from one rod to another, subject to certain rules.

   Approach: Use recursive backtracking to move disks one by one.

2. Rat in a Maze:

   Problem Statement: Find a path for a rat to escape a maze.

   Approach: Use backtracking to explore possible paths.

3. Euler's Totient Function:

   Problem Statement: Calculate the number of positive integers less than or equal to n that are relatively prime to n.

   Approach: Use the formula φ(n) = n (1 - 1/p1) (1 - 1/p2) ... (1 - 1/pk), where p1, p2, ..., pk are prime factors of n.

4. Find Largest Prime Factor of a Number:

   Problem Statement: Find the largest prime factor of a given number.

   Approach: Use a loop to divide the number by increasing integers until it's no longer divisible.

5. Reverse Linked List in Groups of Size K:

   Problem Statement: Reverse a linked list in groups of size k.

   Approach: Use a recursive or iterative approach to reverse each group.

6. N Queen Problem | Return all Distinct Solutions to the N-Queens Puzzle:

   Problem Statement: Place n queens on an nxn chessboard such that no two queens attack each other.

   Approach: Use backtracking to explore possible placements.

7. Fractional Knapsack Problem:

   Problem Statement: Maximize the value of items in a knapsack with limited capacity.

   Approach: Use a greedy algorithm to select items with the highest value-to-weight ratio.

8. K-th Element of two Sorted Arrays:

   Problem Statement: Find the kth element in the union of two sorted arrays.

   Approach: Use binary search or a priority queue.

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These problems cover a wide range of topics in data structures and algorithms. Practicing these problems will help you develop a strong foundation in coding and improve your chances of success in technical interviews.

Recommended Resources:

• GeeksforGeeks

• LeetCode

• HackerRank

• CodeForces

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