Paytm Interview Questions and Answers for Freshers

Q1. Tell me something about yourself
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Q1. Why You want to work in HR?
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Q2. Do you have any prior experience?
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Round duration - 70 Minutes
Round difficulty - Medium

Their were 3 DSA coding questions of medium and hard level. I need to solve them in 70 minutes. Coding questions were of Arrays, Linked list and Binary search trees

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers to keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Q2. 
Problem: Sort an Array of 0s, 1s, and 2s
Given an array/list ARR consisting of integers where each element is either 0, 1, or 2, your task is to sort this array in increasing order.
Input:
The input sta...read more
Ans. 
Sort an array of 0s, 1s, and 2s in increasing order.
• Use a three-pointer approach to sort the array in a single pass.

• Initialize low, mid, and high pointers at the start, iterate through the array, and swap elements accordingly.

• Example: If the current element is 0, swap it with the element at the low pointer and increment both low and mid pointers.
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Round duration - 60 Minutes
Round difficulty - Medium

This round was majorly focused on problem solving skills and DSA. Interviewer asked me three DSA questions of medium and hard level. He started with the hard question, he asked me zig-zag binary tree traversal. we discussed the approach than I coded it and explained its Time and space complexity. Than he asked me max sum subarray modified question, I solved it using Kadane algorithm. Than he discussed one of my online assesments question and asked me to further optimize that approach that I used in the online test. Than I optimized that approach and coded that. Than he asked me for any questions and we dropped the call.

Q1. 
Spiral Order Traversal of a Binary Tree Problem Statement
Given a binary tree with 'N' nodes, your task is to print the nodes in spiral order traversal.
Example:
Input:
The binary tree is represented i...read more
Ans. 
Print nodes of a binary tree in spiral order traversal.
• Use a queue to perform level order traversal.

• Alternate between printing nodes from left to right and right to left at each level.

• Handle null nodes appropriately.

• Example: For input '1 2 3 -1 -1 4 5 -1 -1 -1 -1', the output should be '1 3 2 4 5'.
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Q2. 
Maximum Subarray Sum Problem Statement
Given an array of integers, determine the maximum possible sum of any contiguous subarray within the array.
Example:
Input:
array = [34, -50, 42, 14, -5, 86]
Out...read more
Ans. 
Find the maximum sum of any contiguous subarray within an array of integers.
• Iterate through the array and keep track of the maximum sum of subarrays encountered so far.

• At each index, decide whether to include the current element in the subarray or start a new subarray.

• The maximum subarray sum can be calculated using Kadane's algorithm.

• Example: For array [34, -50, 42, 14, -5, 86], the maximum sum is 137.

• Example: For arr...read more
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Round duration - 40 Minutes
Round difficulty - Medium

This round was mainly focused on operating systems, DBMS and past projects. we started with the introduction. Interviewer asked me explain a functionality of one of my projects that I wrote in my resume, I done that than he started asking OS and DBMS questions. After that we asked me about any bad experience in my past internship, I told that than he asked for any questions to me and we dropped the call and after 2 days I got HR mail that I'm selected.

Round duration - 60 minutes
Round difficulty - Medium

The nature of the interviewer was very kind. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Binary Tree Diameter Problem Statement
Given a binary tree, determine the length of its diameter. The diameter is defined as the longest path between any two end nodes in the tree. The path's length is re...read more
Ans. 
The diameter of a binary tree is the longest path between any two end nodes in the tree.
• Traverse the tree to find the longest path between two leaf nodes.

• Use depth-first search (DFS) to calculate the height of each subtree.

• The diameter is the sum of the heights of the left and right subtrees + 1.
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Q2. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the target minus the element exists in a hash set.

• If it does, add the pair to the result. If not, add the element to the hash set.

• Handle cases where the same element is used twice in a pair.

• Return (-1, -1) if no pair is found.
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Round duration - 35 minutes
Round difficulty - Medium

The nature of the interviewer was very kind, helped me when I stuck. The round was proctored, our webcam and mic were on, and shared my screen.

Round duration - 60 minutes
Round difficulty - Easy

Coding round with 3 coding questions.

Q1. 
Print Nodes at Distance K from a Given Node
Given an arbitrary binary tree, a node of the tree, and an integer 'K', find all nodes that are at a distance K from the specified node, and return a list of th...read more
Ans. 
Given a binary tree, a target node, and an integer K, find all nodes at distance K from the target node.
• Traverse the tree to find the target node.

• From the target node, perform a depth-first search to find nodes at distance K.

• Use a recursive function to keep track of the distance from the target node.

• Return the values of nodes found at distance K in any order.
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Q2. 
Rahul And Minimum Subarray Challenge
Rahul is learning about arrays and lists. His teacher gave him a task to find the length of the smallest subarray in a given array 'ARR' of size 'N' with its sum great...read more
Ans. 
Find the length of the smallest subarray in a given array with sum greater than a given value.
• Iterate through the array while keeping track of the current subarray sum.

• Use two pointers technique to find the smallest subarray with sum greater than X.

• Update the minimum subarray length as you iterate through the array.

• Return the length of the smallest subarray found.

• Example: For ARR = [1, 2, 21, 7, 6, 12] and X = 23, the ...read more
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Q3. 
Encrypt The Digits Problem Statement
Given a numeric string STR consisting of characters from ‘0’ to ‘9’, encrypt the string by replacing each numeric character according to the mapping:
‘0’ -> ‘9’, ‘1’...read more
Ans. 
Encrypt each digit in a numeric string by replacing it with its encrypted equivalent.
• Iterate through each character in the string and replace it with its encrypted equivalent

• Use a mapping to determine the encrypted equivalent of each digit

• Return the encrypted string for each test case
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Round duration - 50 minutes
Round difficulty - Medium

The nature of the interviewer was very kind. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Diagonal Traversal of a Binary Tree
Given a binary tree of integers, find its diagonal traversal. Refer to the example for clarification on diagonal traversal.
Example:
Explanation:
Consider lines at a...read more
Ans. 
Diagonal traversal of a binary tree is finding the nodes in the tree along the diagonals from top-left to bottom-right.
• Traverse the tree in a diagonal manner, starting from the root node and moving towards the right child and then the left child.

• Use a queue to keep track of nodes at each level of the tree.

• Maintain a map to store nodes at each diagonal level and then print the nodes in the map in the required order.
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Q2. 
Parth's OCD Challenge
Parth, a budding programmer, has received an array 'ARR' of 'N' positive integers. His OCD is triggered whenever an odd number appears at an even index or an even number at an odd in...read more
Ans. 
Reorder array to avoid odd numbers at even indices and even numbers at odd indices.
• Swap odd numbers at even indices with the nearest odd number at an odd index, and vice versa.

• Use two pointers approach to iterate through the array and swap elements accordingly.

• Ensure the array has equal numbers of odd integers and odd-index positions and vice-versa.
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Round duration - 50 minutes
Round difficulty - Easy

The nature of the interviewer was very kind. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Subset Sum Equal To K Problem Statement
Given an array/list of positive integers and an integer K, determine if there exists a subset whose sum equals K.
Provide true if such a subset exists, otherwise r...read more
Ans. 
Given an array of positive integers and an integer K, determine if there exists a subset whose sum equals K.
• Use dynamic programming to solve this problem efficiently

• Create a 2D array to store if a subset sum is possible for each element and sum

• Iterate through the array and update the 2D array accordingly

• Check if the subset sum for K is possible at the end
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Q2. 
Next Greater Element Problem Statement
Given a list of integers of size N, your task is to determine the Next Greater Element (NGE) for every element. The Next Greater Element for an element X is the firs...read more
Ans. 
Find the Next Greater Element for each element in a list of integers.
• Iterate through the list of integers from right to left.

• Use a stack to keep track of elements whose NGE is yet to be found.

• Pop elements from the stack until a greater element is found or the stack is empty.

• Assign the NGE as the top element of the stack or -1 if the stack is empty.
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Round duration - 70 minutes
Round difficulty - Easy

Q1. 
Parth's OCD Challenge
Parth, a budding programmer, has received an array 'ARR' of 'N' positive integers. His OCD is triggered whenever an odd number appears at an even index or an even number at an odd in...read more
Ans. 
Reorder array to avoid odd numbers at even indices and even numbers at odd indices.
• Swap odd numbers at even indices with the nearest odd number at an odd index.

• Swap even numbers at odd indices with the nearest even number at an even index.

• Maintain counts of odd and even numbers to ensure equal distribution.
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Q2. 
Find All Occurrences in Matrix
You are provided with a matrix of characters, CHARACTER_MATRIX of size M x N, and a string WORD. Your goal is to locate and display all occurrences of the string within the ...read more
Ans. 
Find all occurrences of a given string in a matrix in all eight possible directions.
• Iterate through each cell in the matrix and check for the starting character of the word.

• For each starting character found, check in all eight directions for the complete word.

• Keep track of the coordinates of each character in the word for each occurrence.

• Print the coordinates of each character for all occurrences found.

• If no occurrence...read more
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Q3. 
Print Nodes at Distance K from a Given Node
Given an arbitrary binary tree, a node of the tree, and an integer 'K', find all nodes that are at a distance K from the specified node, and return a list of th...read more
Ans. 
Given a binary tree, a target node, and an integer K, find all nodes at distance K from the target node.
• Traverse the binary tree to find the target node.

• From the target node, perform a depth-first search to find nodes at distance K.

• Use a recursive function to keep track of the distance from the target node.

• Return the values of nodes found at distance K in any order.
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Round duration - 50 minutes
Round difficulty - Easy

The nature of the interviewer was very kind. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Diagonal Traversal of a Binary Tree
Given a binary tree of integers, find its diagonal traversal. Refer to the example for clarification on diagonal traversal.
Example:
Explanation:
Consider lines at a...read more
Ans. 
Find the diagonal traversal of a binary tree of integers.
• Traverse the binary tree diagonally using a queue and a map to store nodes at each diagonal level.

• Use a depth-first search approach to traverse the tree and populate the map with nodes at each diagonal level.

• Iterate through the map to get the diagonal traversal of the binary tree.
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Q2. 
Binary Tree Diameter Problem Statement
Given a binary tree, determine the length of its diameter. The diameter is defined as the longest path between any two end nodes in the tree. The path's length is re...read more
Ans. 
The diameter of a binary tree is the longest path between any two end nodes in the tree.
• Traverse the tree to find the longest path between two leaf nodes.

• Use depth-first search (DFS) to calculate the height of each subtree.

• The diameter is the sum of the heights of the left and right subtrees + 1.
Answered by AI
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Round duration - 50 minutes
Round difficulty - Medium

The nature of the interviewer was very kind, helped me when I stuck. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Next Greater Element Problem Statement
Given a list of integers of size N, your task is to determine the Next Greater Element (NGE) for every element. The Next Greater Element for an element X is the firs...read more
Ans. 
Find the Next Greater Element for each element in a list of integers.
• Iterate through the list of integers from right to left.

• Use a stack to keep track of elements whose NGE is yet to be found.

• Pop elements from the stack until a greater element is found or the stack is empty.

• Assign the NGE as the top element of the stack or -1 if the stack is empty.

• Repeat the process for all elements in the list to find their NGEs.
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Q2. 
Subset Sum Equal To K Problem Statement
Given an array/list of positive integers and an integer K, determine if there exists a subset whose sum equals K.
Provide true if such a subset exists, otherwise r...read more
Ans. 
Given an array of positive integers and an integer K, determine if there exists a subset whose sum equals K.
• Use dynamic programming to solve this problem efficiently

• Create a 2D array to store if a subset sum is possible for each element and sum

• Iterate through the array and update the 2D array accordingly

• Check if the subset sum for K is possible using the 2D array
Answered by AI
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Round duration - 50 minutes
Round difficulty - Easy

The nature of the interviewer was very kind, helped me when I stuck. The test was proctored, our webcam and mic were on, and shared my screen.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
Ans. 
Given stock prices for 'N' days, find maximum profit with up to two buy-and-sell transactions.
• Iterate through the array of stock prices to find the maximum profit with two transactions

• Keep track of the maximum profit by considering all possible buy and sell combinations

• Ensure to sell the stock before buying again to maximize profit
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