Minimum size subarray sum

Author: volodimyr

209.minimum_size_subarray_sum/min.py

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+#  209. Minimum size subarray sum
+# Topics: 'Sliding Window', 'Prefix Sum', 'Binary Search', 'Array'
+#  Level: 'Medium'
+
+# Given an array of positive integers nums and a positive integer target, return the minimal length of a
+
+# whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.
+
+ 
+
+# Example 1:
+
+# Input: target = 7, nums = [2,3,1,2,4,3]
+# Output: 2
+# Explanation: The subarray [4,3] has the minimal length under the problem constraint.
+
+# Example 2:
+
+# Input: target = 4, nums = [1,4,4]
+# Output: 1
+
+# Example 3:
+
+# Input: target = 11, nums = [1,1,1,1,1,1,1,1]
+# Output: 0
+
+ 
+
+# Constraints:
+
+#     1 <= target <= 109
+#     1 <= nums.length <= 105
+#     1 <= nums[i] <= 104
+
+from typing import List
+
+class Solution:
+    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
+        L = 0
+        min_len = float('inf')
+        window = 0
+        for R in range (len(nums)):
+            window += nums[R]
+
+            while window>=target:
+                min_len = min(min_len, R-L+1)
+                window -= nums[L]
+                L+=1
+            
+        if min_len == float('inf'):
+            return 0
+
+        return min_len

209.minimum_size_subarray_sum/test_min.py

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+import unittest
+from typing import List
+
+from min import Solution
+
+# Assuming your Solution class is already defined above
+class TestMinSubArrayLen(unittest.TestCase):
+
+    def setUp(self):
+        self.solution = Solution()
+
+    def test_example1(self):
+        self.assertEqual(self.solution.minSubArrayLen(7, [2,3,1,2,4,3]), 2)
+
+    def test_example2(self):
+        self.assertEqual(self.solution.minSubArrayLen(4, [1,4,4]), 1)
+
+    def test_example3(self):
+        self.assertEqual(self.solution.minSubArrayLen(11, [1,1,1,1,1,1,1,1]), 0)
+
+    def test_single_element_reach(self):
+        self.assertEqual(self.solution.minSubArrayLen(5, [5]), 1)
+
+    def test_single_element_not_reach(self):
+        self.assertEqual(self.solution.minSubArrayLen(10, [5]), 0)
+
+    def test_entire_array_needed(self):
+        self.assertEqual(self.solution.minSubArrayLen(15, [1,2,3,4,5]), 5)
+
+if __name__ == '__main__':
+    unittest.main()