Python - Search an element in the Doubly Linked List
Searching an element in a doubly linked list requires creating a temp node pointing to the head of the list. Along with this, two more variables are required to track search and track index of the current node. If the temp node is not null at the start, then traverse the list to check if current node value matches with the search value. If it matches then update search tracker variable and stop traversing the list, else keep on traversing the list. If the temp node is empty at the start, then the list contains no item.
The function SearchElement is created for this purpose. It is a 4-step process.
def SearchElement(self, searchValue): #1. create a temp node pointing to head temp = self.head #2. create two variables: found - to track # search, idx - to track current index found = 0 i = 0 #3. if the temp node is not null check the # node value with searchValue, if found # update variables and break the loop, else # continue searching till temp node is not null if(temp != None): while (temp != None): i += 1 if(temp.data == searchValue): found += 1 break temp = temp.next if(found == 1): print(searchValue,"is found at index =", i) else: print(searchValue,"is not found in the list.") else: #4. If the temp node is null at the start, # the list is empty print("The list is empty.")
The below is a complete program that uses above discussed concept to search an element in a given doubly linked list.
# node structure class Node: def __init__(self, data): self.data = data self.next = None self.prev = None #class Linked List class LinkedList: def __init__(self): self.head = None #Add new element at the end of the list def push_back(self, newElement): newNode = Node(newElement) if(self.head == None): self.head = newNode return else: temp = self.head while(temp.next != None): temp = temp.next temp.next = newNode newNode.prev = temp #Search an element def SearchElement(self, searchValue): temp = self.head found = 0 i = 0 if(temp != None): while (temp != None): i += 1 if(temp.data == searchValue): found += 1 break temp = temp.next if(found == 1): print(searchValue,"is found at index =", i) else: print(searchValue,"is not found in the list.") else: print("The list is empty.") #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("The list contains:", end=" ") while (temp != None): print(temp.data, end=" ") temp = temp.next print() else: print("The list is empty.") # test the code MyList = LinkedList() #Add three elements at the end of the list. MyList.push_back(10) MyList.push_back(20) MyList.push_back(30) #traverse to display the content of the list. MyList.PrintList() #search for element in the list MyList.SearchElement(10) MyList.SearchElement(15) MyList.SearchElement(20)
The above code will give the following output:
The list contains: 10 20 30 10 is found at index = 1. 15 is not found in the list. 20 is found at index = 2.