单链表

C语言实现

涉及二级指针内存申请和释放

结构体定义

typedef int32_t DATA_TYPE;

typedef struct {
    DATA_TYPE value;
    struct List *next;
} List;

相关方法实现

#include <stdio.h>
#include <stdbool.h>
#include <inttypes.h>
#include <malloc.h>

/**
 * 创建一个链表，头节点为第零个节点
 * @param head 二级指针 函数内部分配内存
 * @param length 链表长度
 */
void create_list(List **head, int32_t length) {
    *head = (List *) malloc(sizeof(List));
    (*head)->next = NULL;
    List *cur = NULL;
    // 头插法创建链表
    for (int i = 0; i < length; i++) {
        cur = (List *) malloc(sizeof(List));
        cur->value = i + 1;
        cur->next = (*head)->next;
        (*head)->next = (struct List *) cur;
    }
}

/**
 * 在index位置后插入一个节点
 * @param head
 * @param index
 * @param data
 * @return
 */
int insert_element(List *head, int index, DATA_TYPE data) {
    if (!head) {
        return -1;
    }
    int cur = 1;
    List *cur_ptr = (List *) head->next;
    while (cur_ptr && cur < index) {
        cur_ptr = (List *) cur_ptr->next;
        ++cur;
    }
    if (!cur_ptr || cur > index) {
        return -1;
    }
    List *node = (List *) malloc(sizeof(List));
    node->value = data;
    node->next = cur_ptr->next;
    cur_ptr->next = (struct List *) node;
    return 0;
}

int delete_element(List *head, int index, DATA_TYPE *data) {
    if (!head) {
        return -1;
    }
    int cur = 1;
    List *cur_ptr = (List *) head->next;
    while (cur_ptr && cur < index) {
        cur_ptr = (List *) cur_ptr->next;
        ++cur;
    }
    if (!cur_ptr || cur > index) {
        return -1;
    }
    List *q = NULL;
    q = (List *) cur_ptr->next;
    cur_ptr->next = q->next;
    *data = q->value;
    free(q);
    return 0;
}

int32_t get_element(List *head, int32_t index, DATA_TYPE *data) {
    int cur = 0;
    List *cur_ptr = (List *) head->next;
    while (cur_ptr && cur != index) {
        cur_ptr = (List *) cur_ptr->next;
        ++cur;
    }
    if (!cur_ptr || cur > index) {
        return -1;
    }
    *data = cur_ptr->value;
    return 0;
}

int get_size(List *head) {
    if (!head) { return -1; }
    int size = 0;
    List *cur = head;
    while (cur != NULL) {
        cur = (List *) cur->next;
        size++;
    }
    return size;
}

int main() {
    // 链表初始化
    List *head;
    create_list(&head, 10);
    int num;
    get_element(head, 2, &num);
    insert_element(head, 2, 100);
    delete_element(head, 1, &num);
    int size = get_size(head);
    for (int i = 0; i < size; ++i) {
        printf("%d ", head->value);
        head = (List *) head->next;
    }
    // 二级指针申请内存，函数外释放
    free(head);
}

Java语言实现