Create monotonic_array.py (#11025)

* Create monotonic_array.py

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* Update monotonic_array.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: Khushi-Shukla

Diff for: data_structures/arrays/monotonic_array.py

@@ -0,0 +1,23 @@
+# https://leetcode.com/problems/monotonic-array/
+def is_monotonic(nums: list[int]) -> bool:
+    """
+    Check if a list is monotonic.
+
+    >>> is_monotonic([1, 2, 2, 3])
+    True
+    >>> is_monotonic([6, 5, 4, 4])
+    True
+    >>> is_monotonic([1, 3, 2])
+    False
+    """
+    return all(nums[i] <= nums[i + 1] for i in range(len(nums) - 1)) or all(
+        nums[i] >= nums[i + 1] for i in range(len(nums) - 1)
+    )
+
+
+# Test the function with your examples
+if __name__ == "__main__":
+    # Test the function with your examples
+    print(is_monotonic([1, 2, 2, 3]))  # Output: True
+    print(is_monotonic([6, 5, 4, 4]))  # Output: True
+    print(is_monotonic([1, 3, 2]))  # Output: False