Interview Questions

This category contains few tricky questions asked in interviews..

Cursed Trees – Interview Question

Problem Statement This is an awesome interview question which tests our ability to extensively use data structures. We are given an array of trees with different heights. The trees have a curse upon them, they do not grow any more and for a given pair of trees, if a tree is taller than the one to its left then the tree will die in a year. The task at hand is to find out, the number of years after which no trees will die. Explanation Year 1 : At the end of the first year the trees with height 6 , 14 and 10 will die. All of these trees have a smaller tree to their left and the r...
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Merge Point of two Linked Lists

Problem Statement This is another interview question which can be linked to the Cycle Detection in Linked List question. In fact this is an extension of the Cycle Detection problem and requires an extra tweaking. Here is a diagram explaining the the problem of finding the merge point of two linked lists In the above diagram, the head of one linked list is node 1 and the head of another linked list is node 5. The merge point is node 4. We would like to write a program to find node 4 given both the heads. Approach There are multiple ways of solving it, here I list three of them: Br...
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Pattern Search in Grid

Problem Statement Given a huge grid G with M rows and N columns and a pattern P with m rows and n columns. The task at hand is to perform a pattern search in grid, and print YES if the pattern grid P exists in the grid G otherwise print NO [caption id="attachment_3611" align="aligncenter" width="960"] Pattern Search in Grid[/caption] Its a simple string search but requires special attention to the boundary cases. Here is a list of them We only need to test the grid G for M-m rows, because anything below row R-r  cannot accommodate the pattern of size r. We only need to test the gr...
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Ring wise Matrix Rotation

Introduction Matrices have always been of interest in the field of encryption, specifically matrix rotations which leads to a symmetric as well as asymmetric cryptography. To learn more about regular matrix rotation please check my recent posts on the subject. This however is a fancy Ring wise Matrix Rotation and is no where related to the regular rotation of matrices. Problem Statement You are given a M*N grid with the restriction that the minimum of M and N is an even number. Rotate each of the rings by a distance K. We can choose the direction of rotation to be either clockwise or anti-c...
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Cloning Linked List having Next and Random Pointer

Introduction This question was asked by a colleague, although it seems to be simple at first but with given restrictions like running time and space limitations, it becomes tricky. You need to be good with Linked Lists to crack the right solution. Here we try to define the problem in more detail. Given a Linked List where each node contains two pointers next and random. The next pointer points to the immediate next node and the random pointer points to any random node in the linked list. Clone the linked list and return the head of the clone. There are definitely certain conditions impos...
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