Linked list
Linked list is a data structure of computer, which is a kind of physical Storage unit Discontinuous, non sequential storage structure ，data elements The logical order of is through the in the linked list Pointer Link order. The linked list consists of a series of nodes (each element in the linked list is called a node), which can be generated dynamically at run time. Each node consists of two parts: one is storage data elements The other is to store the address of the next node Pointer Domain.
As shown in the figure above, a simple one-way linked list. Visible nodes consist of data and pointers.
There is no pointer in python. We need to replace the pointer with a reference. In the following, we use a pointer, but this is not a pointer, but a reference.
1 class node(): 2 def __init__(self,data=0,next=None): 3 self.data=data 4 self.next=next
As shown in the figure above, the node is created
Then we need to connect the nodes to form a linked list
1 class linklist(): 2 def __init__(self): 3 self.head=None 4 self.len=0
In the linked list, the head node is very important. Generally, the linked list will be traversed from the head node
After referring to some other blogs, we can conclude that we mainly operate the linked list as follows:
1. Add a node at the end of the linked list
2. Insert nodes in the linked list
3. Delete nodes in the linked list
4. Search for nodes in the linked list
5. Modify nodes in the linked list
6. Traverse the output linked list data
1. Add a node at the end of the linked list (the same function as the append() function in the array)
Idea: find the tail node and make the pointer of the tail node next a new node
If the linked list is empty, add a new node directly
1 def append_node(self,data): 2 newnode=node(data,None) 3 temp=self.head 4 if self.head==None: 5 self.head=newnode 6 else : 7 while temp.next!=None: 8 temp=temp.next 9 temp.next=newnode 10 self.len+=1
2. Insert nodes in the linked list
Idea: the new node points to the node at the insertion position, and the previous node at the insertion position points to the new node. If you insert it in the first place, execute only the first half of the sentence
1 def insert(self,number,newdata): 2 temp = self.head 3 j = 0 4 newnode=node(newdata) 5 if self.len < number: 6 print("error") 7 else: 8 while j < number-1: 9 temp = temp.next 10 j += 1 11 newnode.next=temp.next 12 temp.next=newnode 13 self.len+=1
3. Delete nodes in the linked list
Idea: let the node before deleting the node point to the node pointed by the deleted node, and clear the memory occupied by the deleted node. (there is no memory management in python, so the second sentence will not be executed)
1 def del_node(self,number):#The first item is 0 2 temp=self.head 3 j=0 4 if self.len<number: 5 print("error") 6 else: 7 while j<number-1: 8 temp = temp.next 9 j+=1 10 temp.next=temp.next.next 11 self.len-=1
4. Search for nodes in the linked list
Idea: traverse the linked list from the node.
1 def search_node(self,data): 2 temp = self.head 3 j = 0 4 while temp.next!=None: 5 temp = temp.next 6 j += 1 7 if temp.data==data: 8 break 9 return j
5. Modify nodes in the linked list
Idea: traverse the linked list from the first node, find the target node and modify its data.
1 def change_data(self,number,newdata): 2 temp = self.head 3 j = 0 4 if self.len < number: 5 print("error") 6 else: 7 while j < number: 8 temp = temp.next 9 j += 1 10 temp.data=newdata
6. Traverse the output linked list data
Idea: traverse the linked list from the node and output data.
1 def print_list(self): 2 temp=self.head 3 while temp.next!=None: 4 print(temp.data,"-> ",end="") 5 temp=temp.next 6 print(temp.data)
Complete code, please take it if necessary:
1 class node(): 2 def __init__(self,data=0,next=None): 3 self.data=data 4 self.next=next 5 6 class linklist(): 7 def __init__(self): 8 self.head=None 9 self.len=0 10 11 def append_node(self,data): 12 newnode=node(data,None) 13 temp=self.head 14 if self.head==None: 15 self.head=newnode 16 else : 17 while temp.next!=None: 18 temp=temp.next 19 temp.next=newnode 20 self.len+=1 21 22 def print_list(self): 23 temp=self.head 24 while temp.next!=None: 25 print(temp.data,"-> ",end="") 26 temp=temp.next 27 print(temp.data) 28 29 def del_node(self,number):#The first item is 0 30 temp=self.head 31 j=0 32 if self.len<number: 33 print("error") 34 else: 35 while j<number-1: 36 temp = temp.next 37 j+=1 38 temp.next=temp.next.next 39 self.len-=1 40 41 def search_node(self,data): 42 temp = self.head 43 j = 0 44 while temp.next!=None: 45 temp = temp.next 46 j += 1 47 if temp.data==data: 48 break 49 return j 50 51 def change_data(self,number,newdata): 52 temp = self.head 53 j = 0 54 if self.len < number: 55 print("error") 56 else: 57 while j < number: 58 temp = temp.next 59 j += 1 60 temp.data=newdata 61 62 def insert(self,number,newdata): 63 temp = self.head 64 j = 0 65 newnode=node(newdata) 66 if self.len < number: 67 print("error") 68 else: 69 while j < number-1: 70 temp = temp.next 71 j += 1 72 newnode.next=temp.next 73 temp.next=newnode 74 self.len+=1 75 76 a=linklist() 77 for i in range (0,10): 78 a.append_node(i) 79 print("append_node: ",end="") 80 a.print_list() 81 print("del_node(2): ",end="") 82 a.del_node(2) 83 a.print_list() 84 print("search_node(5): ",end="") 85 print(a.search_node(5)) 86 print("change_data(4,999): ",end="") 87 a.change_data(4,999) 88 a.print_list() 89 print("a.insert(4,19909)): ",end="") 90 a.insert(4,19909) 91 a.print_list()