Fixed Size (Subarray Calculation) — Sliding Window
The Fixed Size (Subarray Calculation) pattern applies when you need the Fixed Size (Subarray Calculation) technique within the Sliding Window pattern. Its time complexity is O(n) and space complexity O(1). It is used in 5 problems on Thita, including Calculate Compressed Mean, Find the Power of K-Size Subarrays I and Find X-Sum of All K-Long Subarrays I. Common variations are Character Frequency Matching and Variable Size (Condition-Based).
Learn fixed-size sliding window for subarray calculations like maximum average, moving average, and k-size subarray problems.
Fixed Size (Subarray Calculation) is one of the 4 subpatterns of the Sliding Window pattern, which covers fixed-size, variable-size, and character frequency matching window techniques. The whole pattern is about 2.5 hours of study. This subpattern is a core technique: expect it to come up directly in interviews.
What Fixed Size (Subarray Calculation) covers
Master the sliding window technique for subarray and substring problems. Learn fixed size windows, variable size windows, and monotonic queue optimizations. Problems in this subpattern are usually searched for as fixed window, subarray calculation, maximum average, moving average, k-size subarray, leetcode 643.
How to practise Fixed Size (Subarray Calculation) on Thita.ai
Read the theory for Fixed Size (Subarray Calculation), then work the problems attached to it in the browser editor. Your solution runs against the problem's test cases, and the AI coach offers a hint about the technique you are missing rather than a finished solution. Progress is tracked per subpattern, so the Sliding Window tracker shows this one as covered once you have solved its problems.
Other subpatterns in Sliding Window
- Variable Size (Condition-Based) — Master variable-size sliding window for condition-based problems like longest substring without repeating characters.
- Character Frequency Matching — Learn sliding window with character frequency matching for anagram and permutation substring problems.
- Monotonic Queue for Max/Min — Master monotonic queue (deque) to find maximum or minimum in sliding windows efficiently in O(n) time.
Related DSA patterns
- Two Pointers — Fast-slow, converging, expanding from center, and in-place modification techniques.
- Binary Search Patterns — Standard binary search, rotated arrays, first/last occurrence, and search on answer space.
- Array/Matrix Manipulation Patterns — In-place operations, hashing, prefix sums, spiral traversal, and cyclic sort.
- Linked List Manipulation Patterns — In-place reversal, merging sorted lists, reordering, and intersection detection.
Where to go next
Fixed Size (Subarray Calculation) is one lesson in a 16-pattern DSA course. If you are preparing end to end, work the interview-critical patterns first and use the pattern sheet as the checklist; if you are here for one technique, the Sliding Window guide is the shortest path back to the rest of it.