From 21d54e4774c2f11cf8b50f5e19de46b411edd8e6 Mon Sep 17 00:00:00 2001
From: Omid Rajabi <omid.345@gmail.com>
Date: Tue, 1 Feb 2022 08:53:45 -0500
Subject: [PATCH] added linkedlist swap

---
 src/data-structures/linked-list/LinkedList.js | 57 +++++++++++++++++++
 .../linked-list/LinkedListNode.js             |  8 +++
 src/data-structures/linked-list/README.md     | 45 +++++++++++++++
 3 files changed, 110 insertions(+)

diff --git a/src/data-structures/linked-list/LinkedList.js b/src/data-structures/linked-list/LinkedList.js
index ba7d0e3e..c7e075b0 100644
--- a/src/data-structures/linked-list/LinkedList.js
+++ b/src/data-structures/linked-list/LinkedList.js
@@ -2,6 +2,8 @@ import LinkedListNode from './LinkedListNode';
 import Comparator from '../../utils/comparator/Comparator';
 
 export default class LinkedList {
+  head: any;
+  tail: any;
   /**
    * @param {Function} [comparatorFunction]
    */
@@ -269,4 +271,59 @@ export default class LinkedList {
 
     return this;
   }
+
+  /**
+   * @param {*} value
+   * @return {LinkedList}
+   */
+  swap(data1, data2) {
+    let node1Prev = null;
+    let node2Prev = null;
+    let node1 = this.head;
+    let node2 = this.head;
+  
+    // elements are same, no swap to be made
+    if (data1 === data2) {
+      return;
+    }
+    
+    while (node1 !== null) {
+      if (node1.data === data1) { 
+        break;
+      }
+      node1Prev = node1;
+      node1 = node1.next;
+    }
+    
+    while (node2 !== null) {
+      if (node2.data === data2) {
+        break;
+      }
+      node2Prev = node2;
+      node2 = node2.next;
+    }
+    
+    // swap not possible, one or more element not in list
+    if (node1 === null || node2 === null) {
+      return;
+    }
+  
+    if (node1Prev === null) {
+      this.head = node2;
+    } else {
+      node1Prev.setNextNode(node2);
+    }
+  
+    if (node2Prev === null) { 
+      this.head = node1;
+    } else {
+      node2Prev.setNextNode(node1);
+    }
+    
+    let temp = node1.next;
+    node1.setNextNode(node2.next);
+    node2.setNextNode(temp); 
+  }
+  
+  
 }
diff --git a/src/data-structures/linked-list/LinkedListNode.js b/src/data-structures/linked-list/LinkedListNode.js
index d136e863..d195aa76 100644
--- a/src/data-structures/linked-list/LinkedListNode.js
+++ b/src/data-structures/linked-list/LinkedListNode.js
@@ -7,4 +7,12 @@ export default class LinkedListNode {
   toString(callback) {
     return callback ? callback(this.value) : `${this.value}`;
   }
+
+  setNextNode(node) {
+    if (node instanceof LinkedListNode || node === null) {
+      this.next = node;
+    } else {
+      throw new Error('Next node must be a member of the Node class.');
+    }
+  }
 }
diff --git a/src/data-structures/linked-list/README.md b/src/data-structures/linked-list/README.md
index d4b9fa53..a7adf73c 100644
--- a/src/data-structures/linked-list/README.md
+++ b/src/data-structures/linked-list/README.md
@@ -149,6 +149,51 @@ ReverseTraversal(head, tail)
 end ReverseTraversal
 ```
 
+### Swap
+
+```text
+Swap(head, data1, data2)
+  Pre:  head is the head node in the list
+        data1 and data2 are valid values
+  Post: the 2 items in the list have been swapped
+  if data1 === data2
+    end Swap
+  node1Prev ← null
+  node2Prev ← null
+  node1 ← head
+  node2 ← head
+  while node1 != null
+    if node1.data === data1
+      break
+    node1Prev ← node1
+    node1 ← node1.next
+  end while
+  while node2 != null
+    if node2.data === data2
+      break
+    node2Prev ← node2
+    node2 ← node2.next
+  end while
+  if !node1 or !node2
+    end
+  endif
+  if !node1Prev
+    head ← node2
+  else
+    node1Prev.next ← node2
+  endif
+  if !node2Prev
+    head ← node1
+  else
+    node2Prev.next ← node1
+  endif
+  let temp ← node1.next
+  node1.next ← node2.next
+  node2.next ← temp
+  endSwap
+
+```
+
 ## Complexities
 
 ### Time Complexity