单链表（c++）

一，定义

单链表每个结点储存一个数据和一个指向下一结点的指针，末尾结点指向nullptr。

二，特点

1. 在内存中可以不连续
2. 相比顺序表，插入删除操作效率高，O(1)
3. 查找元素复杂度O(n)

三，操作

1. 定义结点类型

typedef struct node{
    int value;
    node* next {nullptr};
}node, *list;

2. 初始化链表

list init(){
    node* n = (node*)malloc(sizeof(node));
    n->next = nullptr;
    return n;
}

创建链表方法：

list my_list = init();

(头节点不存放数据)

3. 尾插法

void append(list& li, int value){
    //find tail node
    node* target = li;
    for(;target->next != nullptr; target = target->next);
    // create node
    target->next = (node*)malloc(sizeof(node));
    target->next->next = nullptr;
    target->next->value = value;
}

4. 获取链表长度

unsigned len(list& li){
    unsigned length=0;
    for(node* n=li->next; n!=nullptr; n=n->next)
        length++;
    return length;
}

5. 插入

void insert(list& li, unsigned index, int value){
    node* target = li;
    node* new_node = (node*)malloc(sizeof(node));
    //检测输入是否有效
    if(index>len(li)){
        std::cerr << "index out of range" << std::endl;
        return;
    }
    //找到对应位置
    for(unsigned i=0; i<index; i++)
        target = target->next;
    // 插入
    new_node->next = target->next;
    new_node->value = value;
    target->next = new_node;
}

6. 删除结点

void del(list& li, unsigned index){
    node* target = li;
    node* temp=nullptr;
    //检测输入是否有效
    if(index>=len(li)){
        std::cerr << "index out of range" << std::endl;
        return;
    }
    //找到对应位置
    for(unsigned i=0; i<index; i++)
        target = target->next;
    //删除
    temp = target->next;
    target->next = temp->next;
    free(temp);
}

7. 打印链表

void print(list& li){
    node* target = li->next;
    while(target != nullptr){
        std::cout << target->value << ' ';
        target = target->next;
    }
    std::cout << std::endl;
}

四，完整代码

#include <iostream>

typedef struct node{
    int value;
    node* next {nullptr};
}node, *list;

list init(){
    node* n = (node*)malloc(sizeof(node));
    n->next = nullptr;
    return n;
}

unsigned len(list& li){
    unsigned length=0;
    for(node* n=li->next; n!=nullptr; n=n->next)
        length++;
    return length;
}

void print(list& li){
    node* target = li->next; // 方便管理，头节点不存放数据
    while(target != nullptr){
        std::cout << target->value << ' ';
        target = target->next;
    }
    std::cout << std::endl;
}

void append(list& li, int value){
    //find tail node
    node* target = li;
    for(;target->next != nullptr; target = target->next);
    // create node
    target->next = (node*)malloc(sizeof(node));
    target->next->next = nullptr;
    target->next->value = value;
}

void insert(list& li, unsigned index, int value){
    node* target = li;
    node* new_node = (node*)malloc(sizeof(node));
    if(index>len(li)){
        std::cerr << "index out of range" << std::endl;
        return;
    }
    for(unsigned i=0; i<index; i++)
        target = target->next;
    new_node->next = target->next;
    new_node->value = value;
    target->next = new_node;
}

void del(list& li, unsigned index){
    node* target = li;
    node* temp=nullptr;
    if(index>=len(li)){
        std::cerr << "index out of range" << std::endl;
        return;
    }
    for(unsigned i=0; i<index; i++)
        target = target->next;
    
    temp = target->next;
    target->next = temp->next;
    free(temp);
}

int main(){
    list my_list = init();
    int command, index, value;

    std::cout << "single list" << std::endl
    << "0. quit" << std::endl
    << "1. append" << std::endl
    << "2. insert" << std::endl
    << "3. delete" << std::endl
    << "4. print" << std::endl
    << "5. len" << std::endl;

    while(1){
        std::cout << "input command:";
        std::cin >> command;

        if (command==0){
            return 0;
        } else if(command==1) {
            std::cout << "value:";
            std::cin >> value;
            append(my_list, value);
        } else if(command==2) {
            std::cout << "index:";
            std::cin >> index;
            std::cout << "value:";
            std::cin >> value;
            insert(my_list, index, value);
        } else if(command==3) {
            std::cout << "index:";
            std::cin >> index;
            del(my_list, index);
        } else if(command==4) {
            print(my_list);
        } else if(command==5) {
            std::cout << "length:" << len(my_list) << std::endl;
        } else {
            std::cerr << "input error";
        }
    }
    return 0;
}

记录学习过程，如有问题欢迎指出。