Buyhatke Interview Questions, Process, and Tips

2 hours of basic dsa

Q1. What are foreign keys
Ans. 
Foreign keys are columns in a database table that reference the primary key of another table, establishing a relationship between the two tables.
• Foreign keys ensure referential integrity in a database by enforcing relationships between tables.

• They help maintain data consistency by preventing actions that would violate the relationships between tables.

• For example, in a database with tables for 'orders' and 'customers', ...read more
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Q2. Implement depth first search in tree
Ans. 
Depth first search in tree is implemented using recursion to explore each branch fully before moving to the next.
• Start at the root node and recursively visit each child node before moving to the next sibling node.

• Use a stack to keep track of nodes to visit, pushing children onto the stack before siblings.

• Base case is when the current node is null or a leaf node, then backtrack to the parent node.
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Round duration - 90 minutes
Round difficulty - Medium

Q1. 
Time to Burn Tree Problem
You are given a binary tree consisting of 'N' unique nodes and a start node where the burning will commence. The task is to calculate the time in minutes required to completely b...read more
Ans. Using BFS
The idea is to first create an undirected graph of the given binary tree and then doing a bfs traversal of the undirected graph starting from the start node. We will keep a variable ‘count’ that will be incremented at each level of bfs traversal. ‘count-1’ is the required time needed to burn the whole tree.
 
Algorithm
 
• Initialize an unordered map ‘M’ that maps from integer to array of integers that sto...read more
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Q2. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. Dynamic Programming
Approach: In the Dynamic programming we will work considering the same cases as mentioned in the recursive approach. In a DP[][] table let’s consider all the possible weights from ‘1’ to ‘W’ as the columns and weights that can be kept as the rows. 
The state DP[i][j] will denote maximum value of ‘j-weight’ considering all values from ‘1 to ith’. So if we consider ‘wi’ (weight in ‘ith’ row) we can...read more
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Q3. 
Shortest Route Problem Statement
You want to visit your friend’s house located at some position in an infinite grid starting from origin (0, 0). You can move in four directions: East (E), West (W), North ...read more
Ans. Counting
This approach is based on the fact that ‘South’ and ‘North’,  ‘East’ and ‘West’  both are opposite pairs of directions and they can cancel each other's effect.
 
We can simply iterate over the string ‘Str’ and count the number of characters ‘E’, ‘W’, ‘N’, ‘S’ present in the given string.  If the number of ‘E’s in the string ‘Str’ is ‘countE’, number of ‘W’s is ‘countW‘, number of ‘N’s is ‘coun...read more
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