C中的链表 |21xrx.com

C中的链表

2021-07-08 14:41:45 深夜i -- --

C 中的链表

链表是有用的数据结构，具有许多优点。可以在恒定时间内（在双向链表中）在开头或结尾插入新元素。内存利用率是高效的，因为它是在我们向列表中添加新元素时分配的，并且列表大小可以根据需要增加/减少。当列表的大小未知且经常变化时，它们很有用。它使用一个存储数据的节点和一个指向下一个节点的指针。

struct node {
  int data;
  struct node *next;
};

C中的链表程序

#include <stdio.h>
#include <stdlib.h>


struct node {
  int data;
  struct node *next;
};

struct node *start = NULL;
void insert_at_begin(int);
void insert_at_end(int);
void traverse();
void delete_from_begin();
void delete_from_end();
int count = 0;

int main () {
  int i, data;

  for (;;) {
    printf("1. Insert an element at the beginning of linked list.\n");
    printf("2. Insert an element at the end of linked list.\n");
    printf("3. Traverse linked list.\n");
    printf("4. Delete an element from beginning.\n");
    printf("5. Delete an element from end.\n");
    printf("6. Exit\n");

    scanf("%d", &i);

    if (i == 1) {
      printf("Enter value of element\n");
      scanf("%d", &data);
      insert_at_begin(data);
    }
    else if (i == 2) {
      printf("Enter value of element\n");
      scanf("%d", &data);
      insert_at_end(data);
    }
    else if (i == 3)
      traverse();
    else if (i == 4)
      delete_from_begin();
    else if (i == 5)
      delete_from_end();
    else if (i == 6)
      break;
    else
      printf("Please enter valid input.\n");
  }

  return 0;
}

void insert_at_begin(int x) {
  struct node *t;

  t = (struct node*)malloc(sizeof(struct node));
  t->data = x;
  count++;

  if (start == NULL) {
    start = t;
    start->next = NULL;
    return;
  }

  t->next = start;
  start = t;
}

void insert_at_end(int x) {
  struct node *t, *temp;

  t = (struct node*)malloc(sizeof(struct node));
  t->data = x;
  count++;


  if (start == NULL) {
    start = t;
    start->next = NULL;
    return;
  }

  temp = start;

  while (temp->next != NULL)
    temp = temp->next;

  temp->next = t;
  t->next   = NULL;
}

void traverse() {
  struct node *t;

  t = start;

  if (t == NULL) {
    printf("Linked list is empty.\n");
    return;
  }

  printf("There are %d elements in linked list.\n", count);

  while (t->next != NULL) {
    printf("%d\n", t->data);
    t = t->next;
  }
  printf("%d\n", t->data); // Print last node
}


void delete_from_begin() {
  struct node *t;
  int n;

  if (start == NULL) {
    printf("Linked list is empty.\n");
    return;
  }

  n = start->data;
  t = start->next;
  free(start);
  start = t;
  count--;

  printf("%d deleted from the beginning successfully.\n", n);
}

void delete_from_end() {
  struct node *t, *u;
  int n;

  if (start == NULL) {
    printf("Linked list is empty.\n");
    return;
  }

  count--;

  if (start->next == NULL) {
    n = start->data;
    free(start);
    start = NULL;
    printf("%d deleted from end successfully.\n", n);
    return;
  }

  t = start;

  while (t->next != NULL) {
    u = t;
    t = t->next;
  }

  n = t->data;
  u->next = NULL;
  free(t);

  printf("%d deleted from end successfully.\n", n);
}

链表有很多变体，例如最后一个节点包含第一个节点地址的循环链表，每个节点都包含指向前一个和下一个节点的指针的双向链表，以及循环双向链表的循环双向链表。 - 链表。

当预先知道要存储的数据大小并且不会频繁更改时，应使用数组。链表的一个缺点是我们不能像在数组中那样在恒定时间内访问每个元素。了解链表将帮助您学习树数据结构。

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