How should I practice Implement a Queue Using Two Stacks?

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Problem · Stack

Implement a Queue Using Two Stacks

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● EasyOraclePHONE SCREEN

Problem statement

Process a sequence of queue operations while using exactly two stacks as the queue's storage. Do not use a queue data structure.

The arrays operations and values have the same length. At position i:

push adds values[i] to the back of the queue and produces no output.
pop removes the front value and appends its decimal string to the result.
peek reads the front value without removing it and appends its decimal string to the result.
empty appends true or false to the result.

Every pop or peek operation occurs while the queue is non-empty. Return the recorded outputs in operation order.

Function

processQueueOperations(operations: String[], values: int[]) → String[]

Examples

Example 1

operations = ["push","push","peek","pop","empty"]values = [1,2,0,0,0]return = ["1","1","false"]

After pushing 1 and 2, both peek and pop observe the front value 1. Value 2 remains, so the queue is not empty.

Example 2

operations = ["empty","push","empty","peek","pop","empty"]values = [0,7,0,0,0,0]return = ["true","false","7","7","true"]

The queue starts empty. After pushing 7, it is non-empty; peek and pop both return 7, after which it is empty again.

Example 3

operations = ["push","push","pop","push","peek","pop","pop","empty"]values = [-1,-2,0,3,0,0,0,0]return = ["-1","-2","-2","3","true"]

The first pop removes -1. Pushing 3 does not move it ahead of -2, so the next peek and pop return -2. The final pop returns 3.