How to use singly linked lists and circular linked lists in JavaScript

This article mainly introduces the JavaScript data structures of singly linked lists and circular linked lists, and introduces in detail how JavaScript implements singly linked lists and circular linked lists. Those who are interested can learn about the

data structure series. Foreword:

Data structure, as the basic knowledge of programmers, needs to be firmly grasped by each of us. Recently, I have also started a secondary study of data structures to make up for the pits I dug back then. . . . . . When I was in class, I just followed the lectures and did not implement any data structure personally, let alone use data structures to solve problems. Now it’s time to fill the hole. Struggle. I would like to remind the children who read my blog that if you are still in school, never despise the study of any basic course. The hole dug at this time will either need to be filled with double the effort. Either it will directly affect a person's ability, etc. . . . . . Don’t dig a hole for yourself

Let’s get to the point. Regarding the data structure knowledge of linked lists, here is a brief introduction:

Linked lists are non-linear and non-continuous data on physical storage units. Structure (which is linear in data logic), each of its nodes consists of two fields: the data field and the pointer field. The actual data is stored in the data field, and the pointer field stores pointer information, pointing to the next element or the previous element in the linked list. It is precisely because of the existence of pointers that the storage of linked lists is discontinuous in physical units.

The advantages and disadvantages of linked lists are equally obvious. Compared with linear lists, linked lists are more efficient in adding and deleting nodes, because they only need to modify pointer information to complete the operation, unlike linear lists (arrays) that require moving elements. Similarly, the length of a linked list is theoretically infinite (within the memory capacity), and the length can be changed dynamically, which has great advantages over linear lists. Correspondingly, since linear tables cannot randomly access nodes and can only be accessed through pointer traversal queries along the linked list, the efficiency of accessing data elements is relatively low.

The following is the JS part

The common methods and descriptions encapsulated in it:

##isEmpty() Judge whether the linked list is emptysize() Get the length of the linked listtoString()Convert to string outputgetHead()Get the head nodegetTail() Get the tail node

Method	Description
append(element)	Add node element to the end of the linked list
insert(position,element)	Insert node element to position position
removeAt(position)	Delete node according to index value position
remove(element)	Search and delete the given node element
remove()	Delete the last node in the linked list
indexOf(element)	Find and return the index value of the given node element

I won’t write the algorithm descriptions of the commonly used methods here. I believe everyone can easily read and understand them. After all, they are very basic. knowledge.

Singly linked list:

function LinkedList(){ 
 /*节点定义*/ 
 var Node = function(element){ 
  this.element = element; //存放节点内容 
  this.next = null; //指针 
 } 
 
 var length = 0, //存放链表长度 
  head = null; //头指针 
 
 this.append = function(element){ 
  var node = new Node(element), 
   current; //操作所用指针 
 
  if (!head){ 
   head = node; 
  }else { 
   current = head; 
 
   while(current.next){ 
    current = current.next; 
   } 
 
   current.next = node; 
  } 
 
  length++; 
  return true; 
 }; 
 
 this.insert = function(position, element){ 
  if (position >= 0 && position <= length) { 
   var node = new Node(element), 
    current = head, 
    previous, 
    index = 0; 
 
   if(position === 0){ 
    node.next = current; 
    head = node; 
   }else{ 
    while(index++ < position){ 
     previous = current; 
     current = current.next; 
    } 
    node.next = current; 
    previous.next = node; 
   } 
 
   length++; 
   return true; 
  }else{ 
   return false; 
  } 
  }; 
 
 this.removeAt = function(position){ 
  if(position > -1 && position < length){ 
   var current = head, 
    previous, 
    index = 0; 
 
   if (position === 0) { 
 
    head = current.next; 
 
   }else{ 
 
    while (index++ < position){ 
     previous = current; 
     current = current.next; 
    } 
 
    previous.next = current.next; 
   }; 
 
   length--; 
   return current.element; 
  }else{ 
   return null; 
  } 
 }; 
 
 this.remove = function(element){ 
  var current = head, 
   previous; 
 
  if(element === current.element){ 
   head = current.next; 
   length--; 
   return true; 
  } 
  previous = current; 
  current = current.next; 
 
  while(current){ 
   if(element === current.element){ 
    previous.next = current.next; 
    length--; 
    return true; 
   }else{ 
    previous = current; 
    current = current.next; 
   } 
  } 
  return false; 
 }; 
 
 this.remove = function(){ 
  if(length < 1){ 
   return false; 
  } 
 
  var current = head, 
  previous; 
 
  if(length == 1){ 
   head = null; 
   length--; 
   return current.element; 
  } 
 
  
  while(current.next !== null){ 
   previous = current; 
   current = current.next; 
  } 
 
  previous.next = null; 
  length--; 
  return current.element; 
 }; 
 
 this.indexOf = function(element){ 
  var current = head, 
   index = 0; 
 
  while(current){ 
   if(element === current.element){ 
    return index; 
   } 
   index++; 
   current = current.next; 
  } 
 
  return false; 
 }; 
 
 this.isEmpty = function(){ 
  return length === 0; 
 }; 
 
 this.size = function(){ 
  return length; 
 }; 
 
 this.toString = function(){ 
  var current = head, 
   string = &#39;&#39;; 
 
  while(current){ 
   string += current.element; 
   current = current.next; 
  } 
  return string; 
 };  
 
 this.getHead = function(){ 
  return head; 
 } 
  
}

Circular linked list: Based on the singly linked list, pointing the pointer of the tail node to the head node forms a circular linked list. Starting from any node in a circular linked list, the entire linked list can be traversed.

function CircularLinkedList(){ 
 var Node = function(element){ 
  this.element = element; 
  this.next = null; 
 } 
 
 var length = 0, 
  head = null; 
 
 this.append = function(element){ 
  var node = new Node(element), 
   current; 
 
  if (!head) { 
   head = node; 
   node.next = head; 
  }else{ 
   current = head; 
 
   while(current.next !== head){ 
    current = current.next; 
   } 
 
   current.next = node; 
   node.next = head; 
  }; 
 
  length++; 
  return true; 
 }; 
 
 this.insert = function(position, element){ 
  if(position > -1 && position < length){ 
   var node = new Node(element), 
    index = 0, 
    current = head, 
    previous; 
 
 
   if (position === 0) { 
 
    node.next = head; 
    head = node; 
 
   }else{ 
 
    while(index++ < position){ 
     previous = current; 
     current = current.next; 
    } 
 
    previous.next = node; 
    node.next = current; 
 
   }; 
 
   length++; 
   return true; 
  }else{ 
   return false; 
  } 
 }; 
 
 this.removeAt = function(position){ 
  if(position > -1 && position < length){ 
   var current = head, 
    previous, 
    index = 0; 
 
   if (position === 0) { 
 
    head = current.next; 
 
   }else{ 
 
    while (index++ < position){ 
     previous = current; 
     current = current.next; 
    } 
 
    previous.next = current.next; 
   }; 
 
   length--; 
   return current.element; 
  }else{ 
   return null; 
  } 
 }; 
 
 this.remove = function (element){ 
  var current = head, 
   previous, 
   indexCheck = 0; 
 
  while(current && indexCheck < length){ 
   if(current.element === element){ 
    if(indexCheck == 0){ 
     head = current.next; 
     length--; 
     return true; 
    }else{ 
     previous.next = current.next; 
     length--; 
     return true; 
    } 
   }else{ 
    previous = current; 
    current = current.next; 
    indexCheck++; 
   } 
  } 
  return false; 
 }; 
 
 this.remove = function(){ 
  if(length === 0){ 
   return false; 
  } 
 
  var current = head, 
   previous, 
   indexCheck = 0; 
 
  if(length === 1){ 
   head = null; 
   length--; 
   return current.element; 
  } 
 
  while(indexCheck++ < length){ 
   previous = current; 
   current = current.next; 
  } 
  previous.next = head; 
  length--; 
  return current.element; 
 }; 
 
 this.indexOf = function(element){ 
  var current = head, 
   index = 0; 
 
  while(current && index < length){ 
   if(current.element === element){ 
    return index; 
   }else{ 
    index++; 
    current = current.next; 
   } 
  } 
  return false; 
 }; 
 
 
 this.isEmpty = function(){ 
  return length === 0; 
 }; 
 
 this.size = function(){ 
  return length; 
 }; 
 
 this.toString = function(){ 
  var current = head, 
   string = &#39;&#39;, 
   indexCheck = 0; 
 
  while(current && indexCheck < length){ 
   string += current.element; 
   current = current.next; 
   indexCheck++; 
  } 
 
  return string; 
 };  
 
}

Usage method:

Expand the method outside the class:

The above is what I compiled For everyone, I hope it will be helpful to everyone in the future.

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