SDE - 1

A stack is employed to facilitate the greedy decision-making process:
We traverse each digit of num and compare it with the top of the stack (the most recent digit we've chosen to keep).
If the current digit is smaller than the top of the stack and we still have removals (k > 0) remaining, we pop digits from the stack until a suitable position for the current digit is found.
This stack-based approach allows us to maintain the order of digits while dynamically removing larger, less significant digits to form the smallest possible number.

By sorting the array, we can easily place smaller numbers in the even positions and larger numbers in the odd positions. This ensures that the wiggle property is satisfied: numbers at odd positions are greater than their neighbors and numbers at even positions are smaller. The key is to rearrange the array by alternating between the two halves of the sorted array.

Tip 1: Be prepared to handle synchronous calls effectively in your design. 
Tip 2: Focus on optimizing memory usage while implementing the solution. 
Tip 3: Ensure efficient caching mechanisms and avoid generating new URLs for already shortened ones.