Create intersectingListNode.c

Author: careermonk

src/Chapter_03_Linked_Lists/intersectingListNode.c

@@ -0,0 +1,148 @@
+// Copyright (c) 2008 CareerMonk Publications and others.
+// #E-Mail          : info@careermonk.com
+// Creation Date    : 2008-01-10 06:15:46
+// Created by       : Narasimha Karumanchi
+// Book Title       : Data Structures And Algorithms Made Easy
+// Warranty         : This software is provided "as is" without any
+//                    warranty; without even the implied warranty of
+//                    merchantability or fitness for a particular purpose.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/* A structure of linked list ListNode */
+struct ListNode {
+  int data;
+  struct ListNode *next;
+} *head1, *head2;
+
+void initialize(){
+    head1 = NULL;
+    head2 = NULL;
+}
+
+/*
+Given a Inserts a ListNode in pTemp of a singly linked list.
+*/
+void insert(struct ListNode **head, int data) {
+    /* Create a new Linked List ListNode */
+    struct ListNode* newListNode = (struct ListNode*) malloc(sizeof(struct ListNode));
+    newListNode->data  = data;
+    /* Next pointer of new ListNode will point to head ListNode of linked list  */
+    newListNode->next = *head;
+    /* make new ListNode as new head of linked list */
+    *head = newListNode;
+}
+
+int getLength(struct ListNode *head){
+    /* Input Validation */
+    if (head == NULL) {
+       printf("Error : Invalid ListNode pointer !!!\n");
+       return 0;
+    }
+
+    int length =0;
+    while(head != NULL){
+        head = head->next;
+        length++;
+    }
+    return length;
+}
+
+// Prints a linked list from head ListNode till tail ListNode
+void printLinkedList(struct ListNode *head) {
+  while (head != NULL) {
+     printf("%d", head->data);
+     head = head->next;
+     if(head != NULL)
+         printf("-->");
+  }
+}
+
+/* Reverses a given linked list, and return the head pointer of reversed linked list */
+struct ListNode* reverseLinkedList(struct ListNode *head) {
+    struct ListNode *previous, *current, *next;
+    previous = NULL;
+    current = head;
+
+    while (current != NULL) {
+        next  = current->next;
+        current->next = previous;
+        previous = current;
+        current = next;
+    }
+    return previous;
+}
+
+struct ListNode * intersectingListNode(struct ListNode * head1, struct ListNode * head2){
+    // get count of both the lists
+    int m = getLength(head1);
+    int n = getLength(head2);
+
+    //to store the merge point
+    struct ListNode * mergePoint = NULL;
+
+    // finding the value of d based on the longer list
+    int diff = (m > n) ? (m-n) : (n-m);
+
+    //traverse the smaller longer list for 'diff' steps
+    if(m > n){
+        while(diff--)
+            head1 = head1 -> next;
+    }
+    else{
+        while(diff--)
+            head2 = head2 -> next;
+    }
+
+    // now both lists have equal ListNodes till the end.
+    while(head1 && head2){
+        if(head1 -> next->data == head2 -> next->data){
+            mergePoint = head1 -> next;
+            break;
+        }
+
+        head1 = head1 -> next;
+        head2 = head2 -> next;
+    }
+
+    return mergePoint;
+}
+
+int main() {
+  struct ListNode *intersectingNode;
+  initialize();
+  /* Creating a linked List*/
+  insert(&head1, 3);
+  insert(&head1, 8);
+  insert(&head1, 12);
+  insert(&head1, 0);
+  insert(&head1, 35);
+  insert(&head1, 6);
+  insert(&head1, 10);
+  insert(&head1, 350);
+  insert(&head1, 16);
+  insert(&head1, 19);
+  head1 = reverseLinkedList(head1);
+  printf("\nLinked List\n");
+  printLinkedList(head1);
+  insert(&head2, 13);
+  insert(&head2, 18);
+  insert(&head2, 112);
+  insert(&head2, 10);
+  insert(&head2, 135);
+  insert(&head2, 16);
+  insert(&head2, 10);
+  insert(&head2, 350);
+  insert(&head2, 16);
+  insert(&head2, 19);
+  head2 = reverseLinkedList(head2);
+  printf("\nLinked List\n");
+  printLinkedList(head2);
+  intersectingNode = intersectingListNode(head1, head2);
+  if (intersectingListNode)
+    printf("\n Intersecting ListNode is %d", intersectingNode->data);
+  else
+    printf("\n NULL \n");
+  return 0;
+}