# Python program to find the maximum and minimum value node from a doubly linked list.

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## Python program to find the maximum and minimum value node from a doubly linked list.

In this program, we will create a doubly linked list then, iterate through the list to find out the minimum and maximum node.

We will maintain two variables min and max. Min will hold the minimum value node, and max will hold the maximum value node. In the above example, 1 will be the minimum value node and 9 will be the maximum value node

### ALGORITHM:

1. Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
2. Define another class for creating the doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
3. minimumNode() will prints out minimum value node:
• Define variable min and initialize with head’s data.
• Current will point to head.
• Iterate through the list by comparing each node’s data with min.
• If min > current’s data then min will hold current’s data.
• At the end of the list, variable min will hold the minimum value node.
• Print the min value.

a. maximumNode() will prints out maximum value node:

• Define variable max and initialize with head’s data.
• Current will point to head.
• Iterate through the list by comparing each node’s data with max.
• If max < current’s data then max will hold current’s data.
• At the end of the list, variable max will hold the maximum value node.
• Print the max value.

### PROGRAM:

1. #Represent a node of doubly linked list
2. class Node:
3.     def __init__(self,data):
4.         self.data = data;
5.         self.previous = None;
6.         self.next = None;
7. class MinMax:
9.     def __init__(self):
11.         self.tail = None;
14.         #Create a new node
15.         newNode = Node(data);
16.         #If list is empty
18.             #Both head and tail will point to newNode
19.             self.head = self.tail = newNode;
20.             #head’s previous will point to None
22.             #tail’s next will point to None, as it is the last node of the list
23.             self.tail.next = None;
24.         else:
25.             #newNode will be added after tail such that tail’s next will point to newNode
26.             self.tail.next = newNode;
27.             #newNode’s previous will point to tail
28.             newNode.previous = self.tail;
29.             #newNode will become new tail
30.             self.tail = newNode;
31.             #As it is last node, tail’s next will point to None
32.             self.tail.next = None;
33.     #MinimumNode() will find out minimum value node in the list
34.     def minimumNode(self):
35.         #Node current will point to head
37.         #Checks if list is empty
39.             print(“List is empty”);
40.             return 0;
41.         else:
42.             #Initially, min will store the value of head’s data
44.             while(current != None):
45.                 #If value of min is greater than current’s data
46.                 #Then, replace value of min with current node’s data
47.                 if(min > current.data):
48.                     min = current.data;
49.                 current = current.next;
50.         return min;
51.     #MaximumNode() will find out maximum value node in the list
52.     def maximumNode(self):
53.         #Node current will point to head
55.         #Checks if list is empty
57.             print(“List is empty”);
58.             return 0;
59.         else:
60.             #Initially, max will store the value of head’s data
62.             #If value of max is lesser than current’s data
63.             #Then, replace value of max with current node’s data
64.             while(current != None):
65.                 if(current.data > max):
66.                     max = current.data;
67.                 current = current.next;
68.         return max;
69. dList = MinMax();
70. #Add nodes to the list