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

0896_monotonic-array/README.md

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+An array is monotonic if it is either monotone increasing or monotone decreasing.
+
+An array `nums` is monotone increasing if for all `i <= j`, `nums[i] <= nums[j]`. An array `nums` is monotone decreasing if for all `i <= j`, `nums[i] >= nums[j]`.
+
+Given an integer array `nums`, return `true`_if the given array is monotonic, or _`false`_otherwise_.
+
+Example 1:
+    
+    Input: nums = [1,2,2,3] Output: true 
+
+Example 2:
+    
+    Input: nums = [6,5,4,4] Output: true 
+
+Example 3:
+    
+    Input: nums = [1,3,2] Output: false 
+
+Constraints:
+
+* `1 <= nums.length <= 105`
+* `-105 <= nums[i] <= 105`

0896_monotonic-array/python3/solution.py

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+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