Exploring Variants of Sliding window problem

Sliding window problems are a common type of algorithmic problem that involves a list or an array of data. The “window” is a range of elements in the array that usually defined by the start and end indices, i.e., a “sub-array”. The window could either be a fixed or a variable size. Here are a few variants of the sliding window problem:

Fixed Size Sliding Window

This is the simplest variant where the window size is fixed and does not change. The window slides from the start of the array to the end, and at each step, you compute some kind of operation on the elements in the window. An example of this is finding the maximum sum of k consecutive elements in the array.

• Maximum Subarray Sum of Size K (easy)

Variable Size Sliding Window

In this variant, the size of the window can change based on certain conditions. An example of this is finding the longest sub-array that meets a certain condition, like the longest sub-array with sum less than k.

• Longest Substring with At Most K Distinct Characters (medium)
• Minimum Size Subarray Sum (medium)

Sliding Window with Data Structure

Sometimes, a problem may require maintaining a certain data structure within the window, like a set or a map, to quickly check certain conditions. An example of this is finding the longest sub-array with k distinct elements.

• Contains Duplicate II (easy)
• Sliding Window Maximum (hard)

Sliding Window with Two Pointers

This variant involves two pointers where one pointer represents the start of the window and the other represents the end. The pointers can move in the same or opposite directions based on the problem. An example of this is finding a sub-array that meets a certain condition, like a sub-array that sums up to a target value.

• Two Sum II — Input array is sorted (easy)
• Subarray Product Less Than K (medium)

Sliding Window with Maximum/Minimum

This variant involves finding the maximum or minimum value within the window as it slides. An example of this is finding the maximum value in all sub-arrays of size k.

• Sliding Window Maximum (hard)
• Sliding Window Median (hard)

Each of these variants has its own unique characteristics and challenges, but the key idea is the same: you have a window of elements, and you need to compute something as the window slides through the array.