Day 27 More linkedlist problems

Author: mandliya

README.md

@@ -2,9 +2,9 @@
 This repository will contain random algorithm and data structure problems I resolve to solve at least one a day.
 
 ## Current Streak
-**26 days**
+**27 days**
 ## Longest streak
-26  days (August 17, 2015 - Sept 11, 2015)
+27  days (August 17, 2015 - Sept 12, 2015)
 
 ## Include Directiory
 Include directory and sub directories contain STL like header file implementation of various algorithms and data structures. Following header only implementation,
@@ -35,6 +35,9 @@ please let me know.
       Give output as a linked list.
     - Swap nodes of a linkedlist without swapping data
     - Given a linked list, reverse alternate nodes and append at the end
+    - Only given a node pointer, delete the node from the linked list.
+    - Delete the entire linkedlist
+    - Print middle node of linkedlist without iterating twice.
 #### Tree
     - STL like implementation (include dir)
     - Pretty Print of a tree

linked_list_problems/deleteLinkedlist.cpp

@@ -0,0 +1,58 @@
+/**
+ *  Write a simple function to delete a linkedList
+ */
+
+#include <iostream>
+
+struct Node {
+  int data;
+  Node * next;
+  Node( int d ) : data{ d }, next{ nullptr } { }
+};
+
+void insert( Node * & head, int data )
+{
+  Node * newNode = new Node( data );
+  if ( head == nullptr ) {
+    head = newNode;
+  } else {
+    Node * temp = head;
+    while( temp->next != nullptr ) {
+      temp = temp->next;
+    }
+    temp->next = newNode;
+  }
+}
+
+ void printList( Node * head )
+ {
+   while( head ) {
+     std::cout << head->data << "-->";
+     head = head->next;
+   }
+   std::cout << "NULL" << std::endl;
+ }
+
+ void deleteList( Node * & head )
+ {
+    while( head ) {
+      Node * nextNode = head->next;
+      delete( head );
+      head = nextNode;
+    }
+ }
+
+ int main()
+ {
+   Node * head = nullptr;
+  insert( head, 1 );
+  insert( head, 2 );
+  insert( head, 3 );
+  std::cout << "Current  List: ";
+  printList( head );
+  std::cout << "Deleting List \n";
+  deleteList( head );
+  std::cout << "Printing List: ";
+  printList( head );
+  return 0;
+ }

linked_list_problems/deleteNode.cpp

@@ -0,0 +1,63 @@
+#include <iostream>
+
+struct Node {
+  int data;
+  Node * next;
+  Node( int d ) : data{ d }, next{ nullptr } { }
+};
+
+void insert( Node * & head, int data )
+{
+  Node *newNode = new Node(data);
+  if ( head == nullptr ) {
+    head = newNode;
+  } else {
+    Node * temp = head;
+    while ( temp->next != nullptr ) {
+      temp = temp->next;
+    }
+    temp->next = newNode;
+  }
+}
+
+void printList( Node * head )
+{
+  while( head ) {
+    std::cout << head->data << "-->";
+    head = head->next;
+  }
+  std::cout << "NULL" << std::endl;
+}
+
+void deleteNode( Node * node )
+{
+  // return if node is null
+  if ( node == nullptr ) {
+    return;
+  }
+
+  //this method won't work if we are given last node
+  if ( node->next == nullptr ) {
+    return;
+  }
+
+  Node * nextNode = node->next;
+  node->data = nextNode->data;
+  node->next = nextNode->next;
+  delete nextNode;
+}
+
+int main()
+{
+  Node * head = nullptr;
+  insert( head, 1 );
+  insert( head, 12 );
+  insert( head, 2 );
+  insert( head, 3 );
+  insert( head, 4 );
+  printList( head );
+  std::cout << "Deleting node with data 12 \n";
+  deleteNode( head->next );
+  printList( head );
+  return 0;
+}

linked_list_problems/printMiddleNode.cpp

@@ -0,0 +1,60 @@
+/**
+ *  Print middle node of linkedlist in one iteration.
+ */
+
+#include <iostream>
+
+struct Node {
+  int data;
+  Node * next;
+  Node( int d ) : data{ d }, next{ nullptr } { }
+};
+
+void insert( Node * & head, int data )
+{
+  Node * newNode  = new Node( data );
+  if ( head == nullptr ) {
+    head = newNode;
+  } else {
+    Node * temp = head;
+    while( temp->next != nullptr ) {
+      temp = temp->next;
+    }
+    temp->next = newNode;
+  }
+}
+
+void printList( Node * head )
+{
+  while ( head ) {
+    std::cout << head->data << "-->";
+    head = head->next;
+  }
+  std::cout << "NULL" << std::endl;
+}
+
+Node * middleNode( Node * head )
+{
+  Node * fastPtr = head;
+  Node * slowPtr = head;
+  while ( fastPtr != nullptr && fastPtr->next != nullptr) {
+    slowPtr = slowPtr->next;
+    fastPtr = fastPtr->next->next;
+  }
+  return slowPtr;
+}
+
+int main()
+{
+  Node * head = nullptr;
+  insert( head, 1 );
+  insert( head, 2 );
+  insert( head, 3 );
+  insert( head, 4 );
+  insert( head, 5 );
+  printList( head );
+  std::cout << "Middle node is : ";
+  Node * mid = middleNode( head );
+  std::cout << mid->data << std::endl;
+  return 0;
+}