add some array playing

arrays_and_strings/array-check_mountain.py

@@ -0,0 +1,39 @@
+'''
+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] < arr[i]
+arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
+'''
+
+def valid_mountain_array(arr: list[int]) -> bool:
+        
+        last_number, mountain_up = arr[0], True
+        
+        for i, n in enumerate(arr[1:]):
+            
+            if n > last_number:
+                
+                if mountain_up == False:
+                    return False
+                
+            elif n < last_number:
+                
+                if i == 0:
+                    return False
+                mountain_up = False
+            
+            else:
+                return False
+            
+            last_number = n
+        
+        return not mountain_up
+
+
+if __name__ == "__main__":
+    arr = [0,3,2,1]
+    print(valid_mountain_array(arr))