Merge branch 'main' into main

05- May/15- Swapping Nodes in a Linked List/15- Swapping Nodes in a Linked List ( Ibrahim Khalid ).cpp

@@ -0,0 +1,29 @@
+// Author : Ibarhim Khalid
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        // to store values
+        vector<int>v;
+        int cnt=0;
+        ListNode *temp = head;
+        // move between values in linkedlist and store it in vector
+        while(temp !=NULL){
+            v.push_back(temp->val);
+            temp=temp->next;
+        }
+        // swapping the values of the kth node from the beginning and the kth node from the end
+        swap(v[k-1],v[v.size()-k]);
+        // pointer to index in vector
+        int in=0;
+        ListNode *tmp = head;
+        // reorder linkedlist by modified vector
+         while(tmp !=NULL){
+            tmp->val=v[in];
+            cout<<tmp->val<<" ";
+            tmp=tmp->next;
+            in++;
+        }
+
+        return head;
+    }
+};

05- May/15- Swapping Nodes in a Linked List/15- Swapping Nodes in a Linked List (Ahmed Hossam).cpp

@@ -0,0 +1,31 @@
+// Author: Ahmed Hossam
+
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        // Initialize pointers to the head of the list
+        ListNode* one = head;
+        ListNode* two = head;
+        ListNode* curr = head;
+
+        // Calculate the size of the list
+        int sz = 0;
+        while (curr)
+            sz++, curr = curr -> next;
+
+        // Move 'one' pointer to the kth node from the beginning
+        for (int i = 1; i < k; i++)
+            one = one -> next;
+
+        // Move 'two' pointer to the kth node from the end
+        for (int i = 1; i < sz - k + 1; i++)
+            two = two -> next;
+
+        // Swap the values of the two nodes
+        swap(one -> val, two -> val);
+
+        // Return the updated head of the list
+        return head;
+    }
+
+};

05- May/15- Swapping Nodes in a Linked List/15- Swapping Nodes in a Linked List (Omar Sanad).cpp

@@ -0,0 +1,59 @@
+// author : Omar Sanad
+
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+
+        // declare two Nodes one pointing to k_th node from the beginning
+        // the other pointing to k_th node from the end
+        ListNode *FRONT, *BACK;
+
+        // initialize a variable sz to store the length of the linked list
+        int sz = 0;
+
+        // intialize a variable "curr" to keep track the of the curr node while calculating the length of the linked list
+        ListNode* curr = head;
+        while (curr != NULL)
+            curr = curr->next, sz++;
+
+        // initialize a variable "i" to keep track of the idx of the current node .....
+        // while trying to select the k_th node from the beginning and the k_th node from the end
+        int i = 1;
+
+        // update the value of curr to reuse it again while iterating over the linked list
+        curr = head;
+
+        // iterate over the linked list to select the k_th from beginning and the k_th from end
+        while (curr != NULL) {
+
+            // if the current idx == k, then this is the k_th from beginning
+            if (i == k)
+                FRONT = curr;
+
+            // if the current idx == sz - k + 1, then this is the k_th from the end
+            if (i == sz - k + 1)
+                BACK = curr;
+
+            // every iteration we update the curr and i
+            curr = curr->next;
+            i++;
+        }
+
+        // swap the values of the two nodes
+        swap(FRONT->val, BACK->val);
+
+        // return the given list after modifing if
+        return head;
+    }
+};
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     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) {}
+ * };
+ */

05- May/15- Swapping Nodes in a Linked List/15- Swapping Nodes in a Linked List (Osama Ayman).java

@@ -0,0 +1,46 @@
+// Author: Osama Ayman
+// Time: O(n)
+// Space: O(1)
+/**
+ * Definition for singly-linked list.
+ * public 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 swapNodes(ListNode head, int k) {
+        ListNode cur = head, first = head;
+        int size = 1;
+
+        // finding linked list size
+        while(cur != null){
+            // first node
+            if(size == k){
+                first = cur;
+            }
+            size++;
+            cur = cur.next;
+        }
+        int cnt = 1;
+        cur = head;
+        // finding second node that its value needs to be swapped with that of the
+        // first node
+        while(cnt <= size-k){
+
+            // we have found the second node, no need to increment cur again
+            if(cnt == size-k) break;
+            cur = cur.next;
+            cnt++;
+        }
+        System.out.println(first.val + " " + cur.val);
+        // swapping
+        int tmp = cur.val;
+        cur.val = first.val;
+        first.val = tmp;
+        return head;
+    }
+}

05- May/README.md

@@ -35,6 +35,7 @@
 1. **[Solving Questions With Brainpower](#12--solving-questions-with-brainpower)**
 1. **[Count Ways To Build Good Strings](#13--count-ways-to-build-good-strings)**
 1. **[Maximize Score After N Operations](#14--maximize-score-after-n-operations)**
+1. **[Swapping Nodes in a Linked List](#15--swapping-nodes-in-a-linked-list)**
 
 <hr>
 <br><br>
@@ -794,4 +795,52 @@ public:
     }
 };
 ```
+
+<hr>
+<br><br>
+
+## 15)  [Swapping Nodes in a Linked List](https://leetcode.com/problems/swapping-nodes-in-a-linked-list/)
+
+### Difficulty
+
+![](https://img.shields.io/badge/Medium-orange?style=for-the-badge)
+
+### Related Topic
+
+`Linked List` `Two Pointers`
+
+### Code
+
+
+```cpp
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        // Initialize pointers to the head of the list
+        ListNode* one = head;
+        ListNode* two = head;
+        ListNode* curr = head;
+
+        // Calculate the size of the list
+        int sz = 0;
+        while (curr)
+            sz++, curr = curr -> next;
+
+        // Move 'one' pointer to the kth node from the beginning
+        for (int i = 1; i < k; i++)
+            one = one -> next;
+
+        // Move 'two' pointer to the kth node from the end
+        for (int i = 1; i < sz - k + 1; i++)
+            two = two -> next;
+
+        // Swap the values of the two nodes
+        swap(one -> val, two -> val);
+
+        // Return the updated head of the list
+        return head;
+    }
+
+};
+```