Create 941.ValidMountainArray.py

Author: YuriSpiridonov

Easy/941.ValidMountainArray.py

@@ -0,0 +1,48 @@
+'''
+    Given an array of integers arr, return true if and only if it is a 
+    valid mountain array.
+
+    Recall that arr is a mountain array if and only if:
+        - arr.length >= 3
+        - There exists some i with 0 < i < arr.length - 1 such that:
+            =  arr[0] < arr[1] < ... < arr[i - 1] < A[i]
+            =  arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
+
+    Example:
+    Input: arr = [2,1]
+    Output: false
+
+    Example:
+    Input: arr = [3,5,5]
+    Output: false
+
+    Example:
+    Input: arr = [0,3,2,1]
+    Output: true
+
+    Constraints:
+        - 1 <= arr.length <= 10^4
+        - 0 <= arr[i] <= 10^4
+'''
+#Difficulty: Easy
+#52 / 52 test cases passed.
+#Runtime: 188 ms
+#Memory Usage: 15.6 MB
+
+#Runtime: 188 ms, faster than 93.89% of Python3 online submissions for Valid Mountain Array.
+#Memory Usage: 15.6 MB, less than 16.18% of Python3 online submissions for Valid Mountain Array.
+
+class Solution:
+    def validMountainArray(self, arr: List[int]) -> bool:
+        prev = arr[0]
+        left = False
+        top = False
+        for nxt in arr[1:]:
+            if not top and prev < nxt:
+                left = True
+            elif prev > nxt:
+                top = True
+            else:
+                return False
+            prev = nxt
+        return left and top