Program to Find the Largest Element in a Doubly Linked List

• Write a C program to find maximum element of a doubly linked list.
• Function to print largest element of a doubly linked list.

Given a doubly linked list, we have to find maximum value node of a doubly linked list. For Example:

Doubly Linked List
2<-->5<-->9<-->1<-->10<-->1
Maximum Element : 10

In this program, we will use iteration to traverse doubly linked list and search for maximum element.

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Algorithm to find largest node in doubly linked list
Let "head" be the pointer to the head node of given doubly linked list.

• Initialize a variable "max" with data of head node.(max = head->data;)
• Using a loop, traverse doubly linked list until "head" is not equal to NULL.
• For every node, if it's value is larger than max then set max = head->data; else continue.
• At the end of traversal, max will contain the maximum value of given doubly linked list.

In this program, we will use a user defined function "getMaxNode" which takes head pointer of linked list and returns the value of largest node.

int getMaxNode(struct node *head){
    /* Input Validation */
    if(head == NULL){
        printf("Error : Invalid Input !!!!\n");
        return INT_MIN;
    }
    int max = head->data;
    while(head != NULL){
        if(head->data > max){
            max = head->data;
        }
        head = head->next;
    }
    return max;
}

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C program to print largest nodes of a doubly linked list

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
 
/* A structure of Doubly linked list node */
struct node {
  int data;
  struct node *prev, *next;
} *head;

void initialize(){
    head = NULL;
}

/* 
Given a Inserts a node in front of a doubly linked list. 
*/
void insert(int num) {
    /* Create a new Linked List node */
    struct node* newNode = (struct node*) malloc(sizeof(struct node));
    newNode->data  = num;
    /* Insert newNode before head node */
    newNode->next = head;
    newNode->prev = NULL;
    if(head != NULL) {
        head->prev = newNode;
    }
    
    /* Set newNode as head of doubly linked list */
    head = newNode;
    printf("Inserted Element : %d\n", num);
}

int getMaxNode(struct node *head){
    /* Input Validation */
    if(head == NULL){
        printf("Error : Invalid Input !!!!\n");
        return INT_MIN;
    }
    int max = head->data;
    while(head != NULL){
        if(head->data > max){
            max = head->data;
        }
        head = head->next;
    }
    return max;
}
/*
Prints a linked list from head node till tail node 
*/
void printLinkedList(struct node *nodePtr) {
    printf("Doubly Linked List\n");
  while (nodePtr != NULL) {
     printf("%d", nodePtr->data);
     nodePtr = nodePtr->next;
     if(nodePtr != NULL)
         printf("-><-");
  }
}
 
int main() {
    initialize();
    /* Insert elements in Doubly linked list */
    insert(4);  
    insert(9); 
    insert(12); 
    insert(1);
    /* print Doubly Linked list */
    printLinkedList(head);
    /* Printing maximum value node*/
    printf("\nMaximum Value in Linked List : %d", getMaxNode(head));
    
    return 0;
}

Output

Inserted Element : 4
Inserted Element : 9
Inserted Element : 12
Inserted Element : 1
Doubly Linked List
1-><-12-><-9-><-4
Maximum Value in Linked List : 12