# C Exercises: Find maximum value from a doubly linked list

## C Linked List : Exercise-21 with Solution

Write a program in C to find the maximum value from a doubly linked list.
Test Data :
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 9
Input data for node 3 : 1
Expected Output :

``` Data entered in the list are :
node 1 : 5
node 2 : 9
node 3 : 1

The Maximum Value in the Linked List : 9
```

C Code:

```#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

struct node {
int num;
struct node * preptr;
struct node * nextptr;
}*stnode, *ennode;

void DlListcreation(int n);
int getMaxNode(struct node *stnode);
void displayDlList();

int main()
{
int n;
stnode = NULL;
ennode = NULL;
printf("\n\n Doubly Linked List : Find maximum  value from a doubly linked list :\n");
printf("--------------------------------------------------------------------------\n");
printf(" Input the number of nodes : ");
scanf("%d", &n);
DlListcreation(n);
displayDlList();
printf("\n The Maximum Value in the Linked List : %d\n\n", getMaxNode(stnode));
return 0;
}

void DlListcreation(int n)
{
int i, num;
struct node *fnNode;

if(n >= 1)
{
stnode = (struct node *)malloc(sizeof(struct node));

if(stnode != NULL)
{
printf(" Input data for node 1 : "); // assigning data in the first node
scanf("%d", &num);

stnode->num = num;
stnode->preptr = NULL;
stnode->nextptr = NULL;
ennode = stnode;
// putting data for rest of the nodes
for(i=2; i<=n; i++)
{
fnNode = (struct node *)malloc(sizeof(struct node));
if(fnNode != NULL)
{
printf(" Input data for node %d : ", i);
scanf("%d", &num);
fnNode->num = num;
fnNode->preptr = ennode;    // new node is linking with the previous node
fnNode->nextptr = NULL;

ennode->nextptr = fnNode;   // previous node is linking with the new node
ennode = fnNode;            // assign new node as last node
}
else
{
printf(" Memory can not be allocated.");
break;
}
}
}
else
{
printf(" Memory can not be allocated.");
}
}
}

int getMaxNode(struct node *stnode)
{
if(stnode == NULL){
printf(" User message : Invalid Input !!!!\n");
return INT_MIN;
}
int max = stnode->num;
while(stnode != NULL){
if(stnode->num > max){
max = stnode->num;
}
stnode = stnode->nextptr;
}
return max;
}

void displayDlList()
{
struct node * tmp;
int n = 1;
if(stnode == NULL)
{
printf(" No data found in the List yet.");
}
else
{
tmp = stnode;
printf("\n\n Data entered in the list are :\n");

while(tmp != NULL)
{
printf(" node %d : %d\n", n, tmp->num);
n++;
tmp = tmp->nextptr; // current pointer moves to the next node
}
}
}
```

Flowchart :

DlListcreation() :

getMaxNode() :

displayDlList() :

C Practice online:

```
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

struct node {
int num;
struct node * preptr;
struct node * nextptr;
}*stnode, *ennode;

void DlListcreation(int n);
int getMaxNode(struct node *stnode);
void displayDlList();

int main()
{
int n;
stnode = NULL;
ennode = NULL;
printf("\n\n Doubly Linked List : Find maximum  value from a doubly linked list :\n");
printf("--------------------------------------------------------------------------\n");
printf(" Input the number of nodes : ");
scanf("%d", &n);
DlListcreation(n);
displayDlList();
printf("\n The Maximum Value in the Linked List : %d\n\n", getMaxNode(stnode));
return 0;
}

void DlListcreation(int n)
{
int i, num;
struct node *fnNode;

if(n >= 1)
{
stnode = (struct node *)malloc(sizeof(struct node));

if(stnode != NULL)
{
printf(" Input data for node 1 : "); // assigning data in the first node
scanf("%d", &num);

stnode->num = num;
stnode->preptr = NULL;
stnode->nextptr = NULL;
ennode = stnode;
// putting data for rest of the nodes
for(i=2; i<=n; i++)
{
fnNode = (struct node *)malloc(sizeof(struct node));
if(fnNode != NULL)
{
printf(" Input data for node %d : ", i);
scanf("%d", &num);
fnNode->num = num;
fnNode->preptr = ennode;    // new node is linking with the previous node
fnNode->nextptr = NULL;

ennode->nextptr = fnNode;   // previous node is linking with the new node
ennode = fnNode;            // assign new node as last node
}
else
{
printf(" Memory can not be allocated.");
break;
}
}
}
else
{
printf(" Memory can not be allocated.");
}
}
}

int getMaxNode(struct node *stnode)
{
if(stnode == NULL){
printf(" User message : Invalid Input !!!!\n");
return INT_MIN;
}
int max = stnode->num;
while(stnode != NULL){
if(stnode->num > max){
max = stnode->num;
}
stnode = stnode->nextptr;
}
return max;
}

void displayDlList()
{
struct node * tmp;
int n = 1;
if(stnode == NULL)
{
printf(" No data found in the List yet.");
}
else
{
tmp = stnode;
printf("\n\n Data entered in the list are :\n");

while(tmp != NULL)
{
printf(" node %d : %d\n", n, tmp->num);
n++;
tmp = tmp->nextptr; // current pointer moves to the next node
}
}
}
```

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