MEDIUM Sliding Window
209. Minimum Size Subarray Sum
📖 Problem
Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •String/array indexing
- •Set/Map frequency counting
- •Pointer movement invariants
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply Sliding Window reasoning pattern
- •Apply Two Pointers reasoning pattern
💡 Approach
- → Use sliding window with left and right pointers
- → Expand window by moving right pointer
- → When sum >= target, shrink from left and track minimum length
- → All numbers are positive, so shrinking won't increase sum
- → Time: O(n), Space: O(1)
🧭 Prerequisites
🛠️ Hints & Pitfalls
Hints
- •Use sliding window with left and right pointers
- •Expand window by moving right pointer
- •When sum >= target, shrink from left and track minimum length
Common Pitfalls
- •All numbers are positive, so shrinking won't increase sum
- •Time: O(n), Space: O(1)
🧪 Test Cases
Hidden tests on submit: 2
Test Case 1
Not run Input:
minSubArrayLen(7, [2,3,1,2,4,3]); Expected:
2 Test Case 2
Not run Input:
minSubArrayLen(4, [1,4,4]); Expected:
1 Test Case 3
Not run Input:
minSubArrayLen(11, [1,1,1,1,1,1,1,1]); Expected:
0 📝 Code Editor
📤 Output