Two Linked Lists are identical when they have the same data and the arrangement of data is also the same. For example, Linked lists a (1->2->3) and b(1->2->3) are identical. . Write a function to check if the given two linked lists are identical.
Method 1 (Iterative):
To identify if two lists are identical, we need to traverse both lists simultaneously, and while traversing we need to compare data.
C
// An iterative C program to check if // two linked lists are// identical or not#include<stdio.h>#include<stdlib.h>#include<stdbool.h>// Structure for a linked list node struct Node{ int data; struct Node *next;};/* Returns true if linked lists a and b are identical, otherwise false */bool areIdentical(struct Node *a, struct Node *b){ while (a != NULL && b != NULL) { if (a->data != b->data) return false; /* If we reach here, then a and b are not NULL and their data is same, so move to next nodes in both lists */ a = a->next; b = b->next; } // If linked lists are identical, then // 'a' and 'b' must be NULL at this point. return (a == NULL && b == NULL);}/* UTILITY FUNCTIONS TO TEST fun1() and fun2() *//* Given a reference (pointer to pointer) to the head of a list and an int, push a new node on the front of the list. */void push(struct Node** head_ref, int new_data){ // Allocate node struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); // Put in the data new_node->data = new_data; // Link the old list of the new node new_node->next = (*head_ref); // Move the head to point to the // new node (*head_ref) = new_node;}// Driver codeint main(){ /* The constructed linked lists are : a: 3->2->1 b: 3->2->1 */ struct Node *a = NULL; struct Node *b = NULL; push(&a, 1); push(&a, 2); push(&a, 3); push(&b, 1); push(&b, 2); push(&b, 3); areIdentical(a, b)? printf("Identical"): printf("Not identical"); return 0;} |
Output:
Identical
Time Complexity: O(n) where n is the length of the smaller list among a and b.
Method 2 (Recursive):
Recursive solution code is much cleaner than iterative code. You probably wouldn’t want to use the recursive version for production code, however, because it will use stack space which is proportional to the length of the lists.
C
// A recursive C function to check if // two linked lists are identical or notbool areIdentical(struct Node *a, struct Node *b){ // If both lists are empty if (a == NULL && b == NULL) return true; // If both lists are not empty, then // data of current nodes must match, // and same should be recursively true // for rest of the nodes. if (a != NULL && b != NULL) return (a->data == b->data) && areIdentical(a->next, b->next); // If we reach here, then one of the lists // is empty and other is not return false;} |
Time Complexity: O(n) for both iterative and recursive versions. n is the length of the smaller list among a and b.
Auxiliary Space: O(n) for call stack because using recursion
Please refer complete article on Identical Linked Lists for more details!
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