C++ data structure and algorithm inversion linked list method

In this paper, we illustrate the method of C++ data structure and algorithm to reverse the linked list. I will share it with you for your reference as follows:

Algorithm overview: the implementation is required to reverse a single linked list and consider the time complexity.

Algorithm analysis:

Array method (omitted) :

Save the list elements into an array one at a time, and then rebuild the list in reverse
Comments: implementation logic is the simplest and requires additional memory overhead.

Move pointer:

Reverse the pointer to the list element 1 by 1, starting at the head of the list with 3 Pointers
Comments: no additional memory overhead is required to change the original list.

Recursive:

Recursively, the end of the list is found and the pointer is reversed 1 by 1
Comments: no additional memory overhead, no changes to the original linked list.

Algorithm implementation:

Build a linked list structure

/*  The node structure  */
struct NODE
{
 int data;
 struct NODE* next;
};
/*  Add elements - The pressure of stack  */
void push(NODE** head, int dat) {
 struct NODE* new_node = new NODE();
 new_node->data = dat;
 new_node->next = *head;
 *head = new_node;
}
/*  Add elements - add  */
void add(NODE** head, int dat) {
 struct NODE* new_node = new NODE();
 new_node->data = dat;
 new_node->next = NULL;
 if (*head != NULL) {
  struct NODE* temp = *head;
  while (temp->next != NULL) {
   temp = temp->next;
  } 
  temp->next = new_node;
 }
 else {
  *head = new_node;
 }
}

Move the cursor

/*  Inversion of the list  */
void reverse(NODE** head) {
 struct NODE* pre = NULL;
 struct NODE* cur = *head;
 struct NODE* nxt;
 while (cur != NULL) {
  //  Reverse pointer 
  nxt = cur->next;
  cur->next = pre;
  //  Move the cursor 
  pre = cur;
  cur = nxt;
 }
 *head = pre;
}

recursive

/*  Inversion of the list - Copy the original table to return the reverse table  */
NODE* reverse(NODE* head) {
 if (head == NULL || head->next == NULL) {
  return head;
 }
 NODE* new_head = reverse(head->next);
 //  Reverse pointer 
 head->next->next = head;
 head->next = NULL;
 return new_head;
}

Print the list

/*  The print queue  */
void print(NODE* head) {
 NODE* temp = head;
 while (temp != NULL) {
  std::cout << temp->data << std::endl;
  temp = temp->next;
 }
}

The complete code is as follows:

#include <iostream>
/*  The node structure  */
struct NODE
{
  int data;
  struct NODE* next;
};
/*  Add elements - The pressure of stack  */
void push(NODE** head, int dat) {
  struct NODE* new_node = new NODE();
  new_node->data = dat;
  new_node->next = *head;
  *head = new_node;
}
/*  Add elements - add  */
void add(NODE** head, int dat) {
  struct NODE* new_node = new NODE();
  new_node->data = dat;
  new_node->next = NULL;
  if (*head != NULL) {
    struct NODE* temp = *head;
    while (temp->next != NULL) {
      temp = temp->next;
    }  
    temp->next = new_node;
  }
  else {
    *head = new_node;
  }
}
/*  Inversion of the list  */
void reverse(NODE** head) {
  struct NODE* pre = NULL;
  struct NODE* cur = *head;
  struct NODE* nxt;
  while (cur != NULL) {
    //  Reverse pointer 
    nxt = cur->next;
    cur->next = pre;
    //  Move the cursor 
    pre = cur;
    cur = nxt;
  }
  *head = pre;
}
/*  Inversion of the list - Copy the original table to return the reverse table  */
NODE* reverse(NODE* head) {
  if (head == NULL || head->next == NULL) {
    return head;
  }
  NODE* new_head = reverse(head->next);
  //  Reverse pointer 
  head->next->next = head;
  head->next = NULL;
  return new_head;
}
/*  The print queue  */
void print(NODE* head) {
  NODE* temp = head;
  while (temp != NULL) {
    std::cout << temp->data << std::endl;
    temp = temp->next;
  }
}
int main() {
  struct NODE* n = NULL;
  add(&n, 1);
  add(&n, 2);
  add(&n, 3);
  n = reverse(n);
  print(n);
  return 0;
}

I hope this article is helpful to you C++ programming.