<p>An array is <strong>monotonic</strong> if it is either monotone increasing or monotone decreasing.</p>

<p>An array <code>nums</code> is monotone increasing if for all <code>i &lt;= j</code>, <code>nums[i] &lt;= nums[j]</code>. An array <code>nums</code> is monotone decreasing if for all <code>i &lt;= j</code>, <code>nums[i] &gt;= nums[j]</code>.</p>

<p>Given an integer array <code>nums</code>, return <code>true</code><em> if the given array is monotonic, or </em><code>false</code><em> otherwise</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,2,3]
<strong>Output:</strong> true
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [6,5,4,4]
<strong>Output:</strong> true
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,3,2]
<strong>Output:</strong> false
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>5</sup> &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution:
    def isMonotonic(sef, nums: list[int]) -> bool:
        """
        >>> s = Solution()
        >>> s.isMonotonic([1, 2, 3])
        True
        >>> s.isMonotonic([3, 2, 1])
        True
        >>> s.isMonotonic([])
        True
        >>> s.isMonotonic([1, 3, 2])
        False
        """
        if (n := len(nums)) < 2:
            return True
        i = 1
        while i < n and nums[i] == nums[0]:
            i += 1
        if i == n:
            return True
        increasing = nums[i] > nums[0]
        prev = nums[0]
        if increasing:
            while i < n:
                num = nums[i]
                if num < prev:
                    return False
                prev = num
                i += 1
        else:  # not increasing, i.e. "decreasing"
            while i < n:
                num = nums[i]
                if num > prev:
                    return False
                prev = num
                i += 1
        return True
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