Merge pull request #613 from divyaachoudharyy/new_branch

Deleting a node without a head pointer

Author: smv1999

Data Structures/Linked Lists/Singly Linked List/Delete_node_without_head_pointer.cpp

@@ -0,0 +1,110 @@
+/**************************************************
+ 
+ 
+Delete a Node from linked list without head pointer
+ 
+Input: 1->2->3->4->5
+
+Output: 1->2->4->5   //if 3 is to be deleted
+ 
+***************************************************/
+ 
+ //Deleting a node where head pointer is given is very easy, however, 
+ //here we don't have the head pointer and only have the pointer of the node which we want to delete.
+ 
+ //A simple approach would be to have a ptr node that points to the pointer next to deleted node
+ //All you have to do is copy the ptr data into deleted node's data
+ //And do some manipulation with both the pointers.
+ 
+ 
+ //SOLUTION (in C++):
+ 
+ #include<bits/stdc++.h>
+ 
+ using namespace std;
+ 
+ struct Node{
+    int data;
+    struct Node *next;
+    Node(int x){
+        data = x;
+        next = NULL;
+    }
+ }*head = NULL, *ptr = NULL, *temp = NULL;
+ 
+ void create(int value)
+ {
+    if(head == NULL)
+    {
+        head = new Node(value);
+        temp = head;
+    }
+    else
+    {
+        temp->next = new Node(value);
+        temp = temp->next;
+        temp->next = NULL;
+    }
+ }
+ 
+ Node *find_node(struct Node *p, int value)
+ {
+    while(p!=NULL && p->data != value){
+        p = p->next;
+    }
+    return p;
+ }
+ 
+ void deleteNodeWithoutHead(struct Node *del)
+ {
+    if(del == NULL){  //linked list is empty
+        return;
+    }
+    if(del->next == NULL){
+        cout<<"The last node requires head, so it can't be freed"<<endl;
+        return;
+    }
+    ptr = del->next;     // eg: 1->2->3->4->5 suppose del pointer is 3, so,
+                         //  so ptr pointer oints to 4
+                         //now, acc to the code, 1->2->4->4->5
+                         //where the second 4 is ptr after free(ptr), we get,
+                         //1->2->4->5;
+    del->data = del->next->data;
+    del->next = del->next->next;
+    ptr->next = NULL;
+    free(ptr);
+ }
+ 
+ void print(struct Node *node)
+ {
+    while(node!=NULL)
+    {
+        cout<<node->data<<" ";
+        node = node->next;
+    }
+ }
+ 
+ int main()
+ {
+    int n, i, k, data;
+    cout<<"Enter n"<<endl;
+    cin>>n;
+    cout<<"Create a linked list"<<endl;
+    for(i = 0;i<n;i++)
+    {
+        cin>>data;
+        create(data);
+    }
+    cout<<"Enter the value where you want your delete pointer to be"<<endl;
+    cin>>k;
+    // Delete k without sending head
+    Node* del = find_node(head, k);
+    deleteNodeWithoutHead(del);
+ 
+    // Print the final linked list
+    cout<<"Final Linked List after deletion:\n";
+    print(head);
+ 
+    return 0;
+ 
+ }