feat(896-monotonic-array): add py3 soln

0896_monotonic-array/python3/solution.py

@@ -0,0 +1,16 @@
+class Solution:
+    def isMonotonic(self, nums: List[int]) -> bool:
+        direction = 0
+        prev = nums[0]
+        
+        for num in nums[1:]:
+            newDirection = num - prev
+            
+            if direction == 0:
+                direction = newDirection
+            elif direction < 0 < newDirection or direction > 0 > newDirection:
+                return False
+            
+            prev = num
+        
+        return True