Amazon Interview Experience | Set 388 (On -Campus for Full Time)

Round 1: Online coding test – 90 minutes (HackerEarth)

It had 2 coding questions and 20 MCQs.
Q1: Knapsack variation(you can choose an item any number of times)
Q2: Given a 2D array consisting of 0’s, 1’s and 2’s. 1 denotes a fresh apple, 2 denotes a rotten apple and 0 denotes absence of an apple at that position.
Each rotten apple takes 1 day to make it’s neighbors(8, given a fresh apple is already there)
rotten as well. Calculate the number of days when all the apples will be rotten.
If not, then print the number of apples which will never get rotten.
MCQs included some output based questions in C (5), time complexity (2), data structues (10), OS(2), Java based output question(1) etc.

Round 2 (F2F1)
The interviewer was very chilled and asked me to introduce myself, then he asked me to explain any of my projects. He then asked me two questions:
Q1: Given a special binary tree, find the height of the tree.
Speciality: each leaf is connnected to the next leaf(left to right) in a circular doubly linkedlist fashion.
fashion. Let’s say the 2 consequtive leaves are A and B, so, A->right = B and B->left = A. The leftmost leaf’s left points to the right
most leaf and the right most leaf’s right points to the left most leaf.
Expected time complexity = O(n), space complexity = O(1).
Q2: Flip maximum k bits to find the maximize the number of consequtive 1’s in a binary array.
Expected time complexity = O(n), space complexity = O(1).

Round 2 (F2F2)
He started with an description of my projects and then he asked me several questions, majorly:
Q1: Next permutation of a given string(can contain duplicates). (Write complete code including swap, reverse etc).
Q2: Find the mirror the a tree in which each node can have any number of children. (Write complete code)
Q3: Boundary order traversal.
Q4: Check if the given 2 nodes are cousins or not.
Q5: Check wheather a given tree is a summation tree or not. (Any node’s value = sum of all it’s children’s value).

Round 3 (F2F3)
She started with an description of my projects and then he asked me several questions, majorly:
Q1: Difference between recursion and iteration(slightly long discussion).
Q2: Difference between array, linkedlist and trees.
Q3: Discussion on all O(n logn) sorting algorithms.
Q4: Sort an array consisting of 0, 1, and 2’s only in one pass.
Q5: Given 2 arrays which denote the elements to be inserted in two separate binary search trees. Find wheather the two binary search
trees will be same or not, without actually constructing the tree.

        Eg: 2 3 1
            2 1 3
            Ans = Yes.
        Eg. 1 2 3
            3 2 1
            Ans = No. 

Q6: Normal forms in DBMS.
Q7: Difference between threads and processes. Also, between multi threading and multi processing.
Q8: Return a random node from a given binary search tree and also find the k’th smallest value in the tree(can change the structure)
Q9: Spiral order traversal in a square matrix.
Q10: Find an element in a sorted, rotated array. Expected time complexity = O(log n).

Round 4 (Telephonic + screen share)
He also started with an description of my projects. Then he just asked one question.
Q: Given an array, find the number of inversions in the array.
The call quality and the internet connection was poor. I wasn’t able to explain my solution(recurive) on the phone call.
Then I wrote the code on the shared sreen. He asked me to dry run it on a case. Just when I was about to dry run I encountered
a 502 Bad Gateway error. Nevertheless, he could still see my code and asked me questions on some of the things
in my code like the use of “and” instead of “&&” and declaration of array like int temp[n] and not using malloc
(Specifically: why malloc, if you can declare any array like this?). Later, I could not hear him properly so he decided
to end the interview here itself.

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