插入,删除,反转

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

typedef struct Node {
    int data;
    struct Node *next;
}Node, *LinkedList;
//插入方法
LinkedList insert(LinkedList head, Node *node, int index) {
    if (head == NULL) {
        if (index != 0) {
            return head;
        }
        head = node;
        return head;
    }
    if (index == 0) {
        node->next = head;
        head = node;
        return head;
    }
    Node *current_node = head;
    int count = 0;

    while (current_node->next != NULL && count < index - 1) {//双重保证 避免了index超出范围
        current_node = current_node->next;
        count++;
    }
    if (count == index - 1) {//确保能到了指定结点前一个结点
        node->next = current_node->next;
        current_node->next = node;
    }
    return head;
}

//删除结点
LinkedList delete_node(LinkedList head, int index) {
    //1如果头结点为空的话
    if (head == NULL) {
        return head;
    }
    //2如果删除头结点
    if (index == 0) {
        head = head->next;
        return head;
    }
    //其他情况
    Node *current_node = head;
    int count = 0;

    while (current_node->next != NULL && count < index - 1) {
        current_node = current_node->next;
        count++;
    }
    if (count == index - 1) {//记得释放删除结点的内存
        Node *delete_node = current_node->next;
        current_node->next = delete_node->next;
        free(delete_node);
    }

    return head;
}
//链表反转
LinkedList reverse(LinkedList head) {
    if (head == NULL) {
        return head;
    }
    Node *current_node, *next_node; //一个是用来保存当前遍历的结点 一个是用来存储当前遍历结点的下一个结点
    current_node = head->next; //首先移动到第2个结点
    head->next = NULL;//将首结点的下一个结点设置为空

    while (current_node != NULL) {
        next_node = current_node->next;//将当前结点的下一个结点保存起来
        current_node->next = head;//将当前结点的下一个结点设置为头结点
        head = current_node;//将头结点设置为当前结点
        current_node = next_node;//将当前结点进行更新
    }

    return head;
}
//链表内存的清空
void clear(LinkedList head) {
    Node *current_node = head;
    while (current_node != NULL) {
        Node *delete_node = current_node;
        current_node = current_node->next;
        free(delete_node);
    }
}