Amazon SDE Interview Questions and Answers

Construct a binary tree using given preorder and postorder traversals.

• Preorder traversal: Root -> Left -> Right.

• Postorder traversal: Left -> Right -> Root.

• The first element of preorder is the root of the tree.

• The last element of postorder is also the root of the tree.

• To build the tree, recursively find left and right subtrees.

• Example: Preorder: [A, B, D, E, C] and Postorder: [D, E, B, C, A] forms a tre...read more

Find two numbers in an array that add up to a specific target sum.

• Use a hash map to store numbers and their indices for quick lookup.

• Iterate through the array, calculating the complement for each number.

• Example: For nums = [2, 7, 11, 15] and target = 9, return indices [0, 1].

• Time complexity is O(n) due to single pass through the array.

I handle pressure by staying organized, prioritizing tasks, and taking breaks when needed.

• I prioritize tasks based on deadlines and importance

• I break down large tasks into smaller, manageable steps

• I communicate with team members or supervisors if feeling overwhelmed

• I practice mindfulness techniques like deep breathing or meditation to stay calm

Calculate the amount of water that can be trapped between elevation bars after rainfall.

• Use two pointers to traverse the height array from both ends.

• Maintain left and right max heights to calculate trapped water.

• Example: For heights [0,1,0,2,1,0,1,3,2,1,2,1], the trapped water is 6.

A linked list is a data structure consisting of nodes where each node points to the next node in the sequence.

• Create a Node class with data and next pointer

• Initialize a head pointer to null

• Add nodes by updating next pointers

To find a loop in a linked list, use Floyd's Tortoise and Hare algorithm.

• Use two pointers, slow and fast, to traverse the linked list.

• If there is a loop, the two pointers will eventually meet at the same node.

• To find the start of the loop, reset one pointer to the head and move both pointers at the same pace.

Spring is immutable

• Spring framework is immutable

• Once a Spring bean is created, its state cannot be changed

• Any modifications to a Spring bean result in a new instance being created