C/C++——单链表的主要功能实现

　　恰好在复习C/C++，也重新回顾了一下链表，温故而知新，还是有挺大收获的。

　　

/****************************
 * 单链表
 * Author: 玉做的树
 *
 * Node* create() 根据输入创建链表
 * Node* create(int []) 根据数组创建链表
 * const int length(Node *head) 测长
 * void print(Node* head) 输出链表
 * Node* push_back(Node* head, int _data) 尾插入
 * Node* push_front(Node* &head, int _data) 首插入
 * Node* insert(Node* head, int _data, int pos) 特定位置插入
 * void remove(Node** head, int _data) 删除特定值的元素
 * void erase(Node **head, int pos) 删除特定位置的元素
 * Node* sort(Node* head) 排序
 *
 */

#include <iostream>

using namespace std;

struct Node {
    int data;
    Node *next;
    Node() {
        data = 0;
        next = NULL;
    }
    Node(int _data) {
        data = _data;
        next = NULL;
    }
};

// 根据输入创表
Node* create() {
    Node *head, *p1, *p2;
    int _data;
    head = new Node();
    p1 = head;
    
    cout << "Please Input data with space and end with EOF:
";
    while (cin >> _data) {
        p2 = new Node(_data);
        p1->next = p2;
        p1 = p2;
    }
    head = head->next; // 这一步是为了消除头指针未合理利用
    return head;
}

// 根据数组创表
Node* create(int elements[], int len) {
    Node *head, *p1, *p2;
    head = new Node();
    p1 = head;
    
    for (int i = 0; i < len; i++) {
        p2 = new Node(elements[i]);
        p1->next = p2;
        p1 = p2;
    }
    head = head->next; // 这一步是为了消除头指针未合理利用
    return head;
}

// 测长
const int length(Node *head) {
    int len = 0;
    Node* tmp = head;
    while (tmp != NULL) {
        tmp = tmp->next;
        len++;
    }
    return len;
}

// 输出
void print(Node* head) {
    if (head == NULL) {
        cout << "The List is empty!
";
        return;
    }
    int len = length(head);
    Node* tmp = head;
    cout << "The length of the List is " << len << endl;
    
    while (tmp != NULL) {
        cout << tmp->data << " ";
        tmp = tmp->next;
    }
    cout << endl;
}

// 尾插入
Node* push_back(Node* head, int _data) {
    Node *tmp, *tmp2, *newNode;
    tmp = tmp2 = head;
    while (tmp != NULL) {
        tmp2 = tmp; // tmp2用于记录原链表最后一个节点，因为tmp最后指向空，已经不是末尾节点
        tmp = tmp->next;
    }
    newNode = new Node(_data);
    tmp2->next = newNode;
    return newNode;
}

// 头插入, 修改指针要用 ** 或 *&
Node* push_front(Node* &head, int _data) {
    /*       * * 用法
    Node *newNode = new Node(_data);
    newNode->next = *head;
    *head = newNode;
     */
    
    //       * &用法
    Node *newNode = new Node(_data);
    newNode->next = head;
    head = newNode;
    return newNode;
}

// 按position插入
Node* insert(Node* head, int _data, int pos) {
    if (pos < 0 || pos > length(head)) {
        return NULL;
    }
    int count = 0;
    Node* tmp, *tmp2, *newNode;
    tmp = tmp2 = head;
    newNode = new Node(_data);
    while (tmp != NULL && count++ != pos) {
        tmp2 = tmp; // previous one
        tmp = tmp->next;
    }
    if (tmp == head) {
        push_front(head, _data);
    } else if (tmp == NULL) {
        push_back(head, _data);
    } else {
        tmp2->next = newNode;
        newNode->next = tmp;
    }
    return newNode;
}

// 删除所有指定元素
void remove(Node** head, int _data) {
    Node* tmp = *head, *tmp2;
    // 先处理麻烦的头结点
    if (*head != NULL && (*head)->data == _data) {
        *head = (*head)->next;
    }
    while (tmp->next != NULL) {
        tmp2 = tmp;
        tmp = tmp->next;
        if (tmp->data == _data) {
            tmp2->next = tmp->next;
        }
        tmp = tmp2->next;
    }
}

// 删除特定position元素
void erase(Node **head, int pos) {
    Node* tmp = *head, *tmp2 = tmp;
    
    if (pos < 0 || pos > length(*head)) {
        return;
    }
    if (pos == 0 && *head != NULL) {
        *head = (*head)->next;
        delete tmp;
        return;
    }
    while (tmp->next != NULL && pos--) {
        tmp2 = tmp;
        tmp = tmp->next;
    }
    tmp2->next = tmp->next;
    delete tmp;
}

// 排序
Node* sort(Node* head) {
    int len = length(head);
    Node* tmp;
    if (head == NULL || head->next == NULL)
        return head;
    
    for (int i = 0; i < len; i++) {
        tmp = head;
        for (int j = 0; j < len - i - 1; j++) {
            if (tmp->data > tmp->next->data) {
                tmp->data = tmp->data + tmp->next->data;
                tmp->next->data = tmp->data - tmp->next->data;
                tmp->data = tmp->data - tmp->next->data;
            }
            tmp = tmp->next;
        }
    }
    return head;
}

int main() {
    int a[] = {3, 7, 3, 4, 1, 6};
    Node* list = create(a, 6);
    print(list);
    
    sort(list);
    print(list);
    
    /*
    push_back(list, 7);
    print(list);

    push_front(list, 0); // *&用法
    print(list);
    
    insert(list, 2, 1);
    print(list);
    
    remove(&list, 2); // 删除特定值, **用法
    print(list);
    
    erase(&list, 0);
    print(list);
     */
    
    return 0;
}