Created
December 4, 2015 01:38
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#include<stdio.h> | |
#include<stdlib.h> | |
#define true 1 | |
#define false 0 | |
#include <stdio.h> | |
#include <stdlib.h> | |
typedef struct Node { | |
int data; | |
struct Node * next; | |
} Node; | |
Node * createNode(int val){ | |
Node * temp = (Node *)malloc(sizeof(Node)); | |
if(temp){ | |
temp->data = val; | |
temp->next = NULL; | |
} | |
return temp; | |
} | |
/* This function inserts node at the head of linked list */ | |
void push(Node **headRef, int data){ | |
Node * newNode = createNode(data); | |
newNode->next = *headRef; | |
*headRef = newNode; | |
} | |
void printList(Node *head){ | |
while(head){ | |
printf("%d->", head->data); | |
head = head->next; | |
} | |
printf("Null"); | |
} | |
int isPalindromeUtil(Node **forward, Node *backward){ | |
//There are no nodes is lists | |
if(!backward) return true; | |
/*we are recursing moving backward pointer ahead. Backward pointer will | |
start moving backward once we hit above terminal condition of recursion */ | |
int isPalindrome = isPalindromeUtil(forward, backward->next); | |
if(!isPalindrome) return isPalindrome; | |
/*At this point forward is n nodes ahead from start and backward n | |
nodes away from end n varies from 0 to n | |
Compare forwad and backward | |
*/ | |
if((*forward)->data != backward->data){ | |
return false; | |
} | |
//Move ahead forward pointer, backward will move back automatically due to recursion | |
*forward = (*forward)->next; | |
return isPalindrome; | |
} | |
int isPalindromeListRecursiveMethod(Node *head){ | |
/* we are starting with forward pointer and backward at head. | |
Notice that we passing reference to forward and just pointer for | |
backward pointer */ | |
return isPalindromeUtil(&head, head); | |
} | |
int main(void) { | |
Node *head = NULL; | |
push(&head, 3); | |
push(&head, 4); | |
push(&head, 5); | |
push(&head, 6); | |
push(&head, 5); | |
push(&head, 4); | |
push(&head, 2); | |
printf("\nOriginal list :"); | |
printList(head); | |
printf("\nIs list palindrome : %s", isPalindromeListRecursiveMethod(head) ? "true" :"false"); | |
return 0; | |
} |
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