From a31e1879c1b019a09627d8344720cf844579884d Mon Sep 17 00:00:00 2001
From: paisa double <doublepaisa36@gmail.com>
Date: Mon, 6 Oct 2025 10:55:26 +0530
Subject: [PATCH 1/3] Added merge-k-sorted-list algo in linked list section

---
 .../linked_list/merge_k_sorted_list.py        | 92 +++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 data_structures/linked_list/merge_k_sorted_list.py

diff --git a/data_structures/linked_list/merge_k_sorted_list.py b/data_structures/linked_list/merge_k_sorted_list.py
new file mode 100644
index 000000000000..5e5291addd86
--- /dev/null
+++ b/data_structures/linked_list/merge_k_sorted_list.py
@@ -0,0 +1,92 @@
+from __future__ import annotations
+from collections.abc import Iterable, Iterator
+from dataclasses import dataclass
+import heapq
+
+
+test_data_odd = (3, 9, -11, 0, 7, 5, 1, -1)
+test_data_even = (4, 6, 2, 0, 8, 10, 3, -2)
+test_data_mixed = (1, 4, 7), (2, 5, 8), (3, 6, 9)
+
+
+@dataclass
+class Node:
+    data: int
+    next_node: Node | None
+
+
+class SortedLinkedList:
+    def __init__(self, ints: Iterable[int]) -> None:
+        self.head: Node | None = None
+        for i in sorted(ints, reverse=True):
+            self.head = Node(i, self.head)
+
+    def __iter__(self) -> Iterator[int]:
+        node = self.head
+        while node:
+            yield node.data
+            node = node.next_node
+
+    def __len__(self) -> int:
+        return sum(1 for _ in self)
+
+    def __str__(self) -> str:
+        return " -> ".join([str(node) for node in self])
+
+
+def merge_two_lists(
+    sll_one: SortedLinkedList, sll_two: SortedLinkedList
+) -> SortedLinkedList:
+    """Merge two sorted linked lists."""
+    return SortedLinkedList(list(sll_one) + list(sll_two))
+
+
+def merge_k_sorted_lists(lists: list[SortedLinkedList]) -> SortedLinkedList:
+    """
+    Merge k sorted linked lists into one sorted linked list.
+    
+    >>> SSL = SortedLinkedList
+    >>> lists = [SSL([1, 4, 7]), SSL([2, 5, 8]), SSL([3, 6, 9])]
+    >>> merged = merge_k_sorted_lists(lists)
+    >>> str(merged)
+    '1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9'
+    >>> len(merged)
+    9
+    """
+    # Create a min-heap (stores tuples of value, index, node)
+    heap: list[tuple[int, int, Node]] = []
+    for i, sll in enumerate(lists):
+        if sll.head:
+            heapq.heappush(heap, (sll.head.data, i, sll.head))
+
+    dummy = Node(0, None)
+    current = dummy
+
+    while heap:
+        value, idx, node = heapq.heappop(heap)
+        current.next_node = Node(value, None)
+        current = current.next_node
+
+        if node.next_node:
+            heapq.heappush(heap, (node.next_node.data, idx, node.next_node))
+
+    # Convert to SortedLinkedList for consistency
+    result = SortedLinkedList([])
+    result.head = dummy.next_node
+    return result
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+    SSL = SortedLinkedList
+
+    # Example usage
+    list1 = SSL(test_data_odd)
+    list2 = SSL(test_data_even)
+    list3 = SSL([-15, -10, -5, 0, 5])
+    merged_k = merge_k_sorted_lists([list1, list2, list3])
+
+    print("Merged K Sorted Lists:")
+    print(merged_k)

From cd20b4de5180507fc44db8713ce8f86bd57fe077 Mon Sep 17 00:00:00 2001
From: paisa double <doublepaisa36@gmail.com>
Date: Mon, 6 Oct 2025 11:02:10 +0530
Subject: [PATCH 2/3] added reference and desc for merge_k_sorted_list algo

---
 .../linked_list/merge_k_sorted_list.py        | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/data_structures/linked_list/merge_k_sorted_list.py b/data_structures/linked_list/merge_k_sorted_list.py
index 5e5291addd86..3f4a0ad70644 100644
--- a/data_structures/linked_list/merge_k_sorted_list.py
+++ b/data_structures/linked_list/merge_k_sorted_list.py
@@ -1,3 +1,21 @@
+""" This algorithm merges k sorted linked lists into a single sorted linked list.
+
+Each input linked list is assumed to be sorted in non-decreasing order. The algorithm uses a min-heap (priority queue) to efficiently determine the next smallest node among all the heads of the lists.
+
+At every step:
+
+The smallest element among the current nodes of all lists is extracted from the heap.
+
+That node is appended to the result list.
+
+The next node from the same list (if any) is then pushed into the heap.
+
+This process repeats until all nodes from all lists have been processed.
+The final result is a single sorted linked list containing all elements from the input lists.
+
+Solve on:
+https://leetcode.com/problems/merge-k-sorted-lists/
+"""
 from __future__ import annotations
 from collections.abc import Iterable, Iterator
 from dataclasses import dataclass
@@ -90,3 +108,6 @@ def merge_k_sorted_lists(lists: list[SortedLinkedList]) -> SortedLinkedList:
 
     print("Merged K Sorted Lists:")
     print(merged_k)
+
+'''
+'''
\ No newline at end of file

From 7051feed4233926f661ff2a342c8084e70df0292 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 6 Oct 2025 05:34:38 +0000
Subject: [PATCH 3/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 data_structures/linked_list/merge_k_sorted_list.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/data_structures/linked_list/merge_k_sorted_list.py b/data_structures/linked_list/merge_k_sorted_list.py
index 3f4a0ad70644..6a88586c3636 100644
--- a/data_structures/linked_list/merge_k_sorted_list.py
+++ b/data_structures/linked_list/merge_k_sorted_list.py
@@ -1,4 +1,4 @@
-""" This algorithm merges k sorted linked lists into a single sorted linked list.
+"""This algorithm merges k sorted linked lists into a single sorted linked list.
 
 Each input linked list is assumed to be sorted in non-decreasing order. The algorithm uses a min-heap (priority queue) to efficiently determine the next smallest node among all the heads of the lists.
 
@@ -16,6 +16,7 @@
 Solve on:
 https://leetcode.com/problems/merge-k-sorted-lists/
 """
+
 from __future__ import annotations
 from collections.abc import Iterable, Iterator
 from dataclasses import dataclass
@@ -62,7 +63,7 @@ def merge_two_lists(
 def merge_k_sorted_lists(lists: list[SortedLinkedList]) -> SortedLinkedList:
     """
     Merge k sorted linked lists into one sorted linked list.
-    
+
     >>> SSL = SortedLinkedList
     >>> lists = [SSL([1, 4, 7]), SSL([2, 5, 8]), SSL([3, 6, 9])]
     >>> merged = merge_k_sorted_lists(lists)
@@ -109,5 +110,5 @@ def merge_k_sorted_lists(lists: list[SortedLinkedList]) -> SortedLinkedList:
     print("Merged K Sorted Lists:")
     print(merged_k)
 
-'''
-'''
\ No newline at end of file
+"""
+"""