Problem Challenge 3: Frequency Stack (hard)

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Problem Challenge 3: Frequency Stack (hard)

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Problem Statement

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

push(int num): Pushes the number ‘num’ on the stack.
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

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