Given N elements and the task is to implement a stack which removes and returns the maximum frequency element on every pop operation. If there’s a tie in the frequency then the topmost highest frequency element will be returned.
pop() -> returns 6, as 6 is the most frequent (frequency of 6 = 2 ).
pop() -> returns 8 (6 also has the highest frequency but it is not the topmost)
Approach: Maintaining two HashMap, one is frequency HashMap which maps elements to their frequencies and other is setMap which maps all the element with same frequency in one group (Stack).
FrequencyStack has 2 functions:
- push(int x): map the element (x) with frequency HashMap and update the maxfreq variable ( i.e. holds the maximum frequency till now ). setMap maintains a stack which contains all the elements with same frequency.
- pop(): First get the maxfreq element from setMap and then decrement the frequency of the popped element. After popping, if the stack becomes empty then decrement the maxfreq.
Below is the implementation of the above approach:
- Design a stack with operations on middle element
- Maximum difference between frequency of two elements such that element having greater frequency is also greater
- Design a stack to retrieve original elements and return the minimum element in O(1) time and O(1) space
- Tracking current Maximum Element in a Stack
- Replace each element by the difference of the total size of the array and frequency of that element
- Find maximum in stack in O(1) without using additional stack
- Sudo Placement[1.3] | Stack Design
- Design a stack that supports getMin() in O(1) time and O(1) extra space
- Sliding Window Maximum (Maximum of all subarrays of size k) using stack in O(n) time
- Next Greater Frequency Element
- Design and Implement Special Stack Data Structure | Added Space Optimized Version
- Find the element having different frequency than other array elements
- Python | Element with largest frequency in list
- Cumulative frequency of count of each element in an unsorted array
- Frequency of each element of an array of small ranged values
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