Merge pull request #1157 from Hemav009/ll

Added leetode 92 solution

Author: ajay-dhangar

dsa-solutions/lc-solutions/0000-0099/0092-Reverse-LinkedList-II.md

@@ -0,0 +1,241 @@
+---
+id: reverse-linked-list-II
+title: Reverse Linked List II
+sidebar_label: 0092 - Reverse Linked List II
+tags:
+  - Linked List
+  - Leetcode
+description: "This is a solution to the Reverse Linked List II problem on LeetCode."
+---
+
+## Problem Statement
+
+Given the head of a singly linked list and two integers left and right where `left <= right`, reverse the nodes of the list from position left to position right, and return the reversed list.
+
+### Examples
+
+**Example 1:**
+
+```
+Input: head = [1,2,3,4,5], left = 2, right = 4
+Output: [1,4,3,2,5]
+```
+
+**Example 2:**
+
+```
+Input: head = [5], left = 1, right = 1
+Output: [5]
+```
+
+### Constraints:
+
+- The number of nodes in the list is `n`.
+- $1 <= n <= 500$
+- $-500 <= Node.val <= 500$
+- $1 <= left <= right <= n$
+
+### Algorithm
+
+1. Create a dummy node pointing to the head of the list to handle edge cases easily.
+2. Find the node just before the `left` position (`leftNode`) and the node at the `left` position (`curr`).
+3. Reverse the sublist from `left` to `right`.
+4. Reconnect the reversed sublist back to the list.
+5. Return the new head of the list (`dummy.next`).
+
+### Pseudocode
+
+```
+function reverseLinkedList(head, left, right):
+    if head is null:
+        return null
+
+    dummy = new ListNode(0)
+    dummy.next = head
+    leftNode = dummy
+    curr = head
+
+    for i from 0 to left-2:
+        leftNode = leftNode.next
+        curr = curr.next
+
+    subhead = curr
+    preNode = null
+
+    for i from 0 to right-left:
+        nextNode = curr.next
+        curr.next = preNode
+        preNode = curr
+        curr = nextNode
+
+    leftNode.next = preNode
+    subhead.next = curr
+
+    return dummy.next
+```
+
+### Python
+
+```python
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+class Solution:
+    def reverseLinkedList(self, head: ListNode, left: int, right: int) -> ListNode:
+        if not head:
+            return None
+
+        dummy = ListNode(0)
+        dummy.next = head
+        leftNode = dummy
+        curr = head
+
+        for i in range(left - 1):
+            leftNode = leftNode.next
+            curr = curr.next
+
+        subhead = curr
+        preNode = None
+
+        for i in range(right - left + 1):
+            nextNode = curr.next
+            curr.next = preNode
+            preNode = curr
+            curr = nextNode
+
+        leftNode.next = preNode
+        subhead.next = curr
+
+        return dummy.next
+```
+
+### Java
+
+```java
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode() {}
+    ListNode(int val) { this.val = val; }
+    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+}
+
+class Solution {
+    public ListNode reverseLinkedList(ListNode head, int left, int right) {
+        if (head == null) return null;
+
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode leftNode = dummy;
+        ListNode curr = head;
+
+        for (int i = 0; i < left - 1; i++) {
+            leftNode = leftNode.next;
+            curr = curr.next;
+        }
+
+        ListNode subhead = curr;
+        ListNode preNode = null;
+
+        for (int i = 0; i <= right - left; i++) {
+            ListNode nextNode = curr.next;
+            curr.next = preNode;
+            preNode = curr;
+            curr = nextNode;
+        }
+
+        leftNode.next = preNode;
+        subhead.next = curr;
+
+        return dummy.next;
+    }
+}
+```
+
+### C++
+
+```cpp
+class ListNode {
+public:
+    int val;
+    ListNode *next;
+    ListNode() : val(0), next(nullptr) {}
+    ListNode(int x) : val(x), next(nullptr) {}
+    ListNode(int x, ListNode *next) : val(x), next(next) {}
+};
+
+class Solution {
+public:
+    ListNode* reverseLinkedList(ListNode* head, int left, int right) {
+        if (!head) return nullptr;
+
+        ListNode* dummy = new ListNode(0);
+        dummy->next = head;
+
+        ListNode* leftNode = dummy;
+        ListNode* curr = head;
+
+        for (int i = 0; i < left - 1; i++) {
+            leftNode = leftNode->next;
+            curr = curr->next;
+        }
+
+        ListNode* subhead = curr;
+        ListNode* preNode = nullptr;
+
+        for (int i = 0; i <= right - left; i++) {
+            ListNode* nextNode = curr->next;
+            curr->next = preNode;
+            preNode = curr;
+            curr = nextNode;
+        }
+
+        leftNode->next = preNode;
+        subhead->next = curr;
+
+        return dummy->next;
+    }
+};
+```
+
+### JavaScript
+
+```javascript
+class ListNode {
+  constructor(val = 0, next = null) {
+    this.val = val;
+    this.next = next;
+  }
+}
+
+var reverseLinkedList = function (head, left, right) {
+  if (!head) return null;
+
+  let dummy = new ListNode(0);
+  dummy.next = head;
+  let leftNode = dummy;
+  let curr = head;
+
+  for (let i = 0; i < left - 1; i++) {
+    leftNode = leftNode.next;
+    curr = curr.next;
+  }
+
+  let subhead = curr;
+  let preNode = null;
+
+  for (let i = 0; i <= right - left; i++) {
+    let nextNode = curr.next;
+    curr.next = preNode;
+    preNode = curr;
+    curr = nextNode;
+  }
+
+  leftNode.next = preNode;
+  subhead.next = curr;
+
+  return dummy.next;
+};
+```