Fix negative indexing bug and improve readability in wiggle_sort (#15371)

* Fix negative indexing bug and improve readability in wiggle_sort

Issue:
- The previous implementation used `enumerate(nums)`, starting the loop at `i = 0`. This caused `nums[i - 1]` to evaluate to `nums[-1]`, accidentally comparing (and potentially swapping) the first element with the last element of the array on the first iteration.
- The conditional logic `(i % 2 == 1) == (nums[i - 1] > nums[i])` was convoluted, hard to read, and triggered unnecessary swaps when adjacent numbers were equal.

Fix:
- Changed the loop to use `range(1, len(nums))` to ensure the index safely starts at 1, eliminating the negative indexing bug.
- Replaced the confusing equality check with explicit `if/elif` statements that clearly define the peak (odd indices) and valley (even indices) requirements of a Wiggle Sort. 
- Preserved all original docstrings and the __main__ block as-is.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Combine conditional branches to satisfy ruff linting

- Updated `wiggle_sort` logic to merge the odd and even swap conditions using a single `or` expression.
- Fixes SIM114 ruff linter check failure (`Combine if branches using logical or operator`).

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update doctests in wiggle_sort to match fixed implementation output

- Updated expected outputs for negative array doctests in `sorts/wiggle_sort.py`.
- The previous doctest expectations relied on the incorrect behavior caused by the index-0 negative lookup bug.
- Fixes pytest doctest mismatch failure in CI build job.

---------

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

Author: Ewanjohndennis

sorts/wiggle_sort.py

@@ -11,19 +11,23 @@
 
 def wiggle_sort(nums: list) -> list:
     """
-    Python implementation of wiggle.
+    Python implementation of wiggle sort.
+    Reorders an array such that nums[0] <= nums[1] >= nums[2] <= nums[3]...
+
     Example:
     >>> wiggle_sort([0, 5, 3, 2, 2])
     [0, 5, 2, 3, 2]
     >>> wiggle_sort([])
     []
     >>> wiggle_sort([-2, -5, -45])
-    [-45, -2, -5]
+    [-5, -2, -45]
     >>> wiggle_sort([-2.1, -5.68, -45.11])
-    [-45.11, -2.1, -5.68]
+    [-5.68, -2.1, -45.11]
     """
-    for i, _ in enumerate(nums):
-        if (i % 2 == 1) == (nums[i - 1] > nums[i]):
+    for i in range(1, len(nums)):
+        if (i % 2 == 1 and nums[i - 1] > nums[i]) or (
+            i % 2 == 0 and nums[i - 1] < nums[i]
+        ):
             nums[i - 1], nums[i] = nums[i], nums[i - 1]
 
     return nums