Grokking the Coding Interview: Patterns for Coding Questions
Ask Author
Back to course home

0% completed

Vote For New Content
Problem Challenge 3: Frequency Stack (hard)
On this page

Problem Statement

Try it yourself

Problem Statement

Design a class that simulates a Stack data structure, implementing the following two operations:

  1. push(int num): Pushes the number ‘num’ on the stack.
  2. pop(): Returns the most frequent number in the stack. If there is a tie, return the number which was pushed later.

Example:

After following push operations: push(1), push(2), push(3), push(2), push(1), push(2), push(5)

1. pop() should return 2, as it is the most frequent number
2. Next pop() should return 1
3. Next pop() should return 2

Constraints:

  • 0 <= val <= 10<sup>9</sup>
  • At most 2 * 10<sup>4</sup> calls will be made to push and pop.
  • It is guaranteed that there will be at least one element in the stack before calling pop.

Try it yourself

Try solving this question here:

Python3
Python3
. . . .

.....

.....

.....

Like the course? Get enrolled and start learning!

On this page

Problem Statement

Try it yourself