209. Minimum Size Subarray Sum

Author: papilo-cloud

Sliding_Window/min_sub_array_len.py

@@ -0,0 +1,51 @@
+# 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.
+
+ 
+
+# 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
+ 
+
+# Follow up: If you have figured out the O(n) solution, try coding another solution of
+# which the time complexity is O(n log(n)).
+
+
+from typing import List
+class Solution:
+    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
+        prefix_sum = left = 0
+        ln = len(nums)
+        ans = ln + 1
+
+        for i in range(ln):
+            prefix_sum += nums[i]
+            while prefix_sum >= target:
+                ans = min(ans, i - left + 1)
+                prefix_sum -= nums[left]
+                left += 1
+        if ans > ln:
+            return 0
+        else:
+            return ans