链表

2021-01-06 本文已影响0人 lieon

线性表是具有 n 个相同类型元素的有限序列（ n ≥ 0 ）

常见的线性表有
数组
链表
栈
队列
哈希表（散列）

动态数组的缺点

可能会造成大量的内存浪费

链表

链表是一种链式存储的线性表，所有元素的内存地址不一定是连续的
在接口设计时：从表头，表尾，中间入手, 表头的特殊情况有： index == 0 && size == 0, index == 0 && size == 1，表尾的特殊情况有： index == size && size == 1, 确定链表结构后，接口的设计可手动把链表的数据流程画出来，这样接口的逻辑就很清晰了

image.png

单向链表


template<typename E>
class LinkedList: public AbstractList<E> {
    template<typename Element>
    class Node {
    public:
        Element element ;
        Node<Element> *next { nullptr };
        
        Node(const Element &element, Node<Element> * const next) {
            this->element = element;
            this->next = next;
        }
 
      ~Node() {
       }
    };
    
private:
    Node<E> *first { nullptr };
    
    // 获取index位置对应的节点对象
    Node<E> & nodeAt(int index) {
        this->rangeCheck(index);
        Node<E> *node = first;
        for (int i = 0; i < index; i++) {
            node = node->next;
        }
        return *node;
    }
public:
    LinkedList() {
        this->m_size = 0;
    }
    
   ~LinkedList() {
        clear();
    }
    
    void clear() override {
        this->m_size = 0;
        if (first != nullptr) {
            delete first;
            first = nullptr;
        }
    }
    
    bool contains(const E &element) override {
        return false;
    }
    
    E& set(int index, const E &element) override {
        Node<E> &node = nodeAt(index);
        E& old = node.element;
        node.element = element;
        return old;
    }
    
    void insert(int index, const E &element) override {
        if (index == 0) {
            first = new Node<E>(element, first);
        } else {
            Node<E> &prev = nodeAt(index - 1);
            Node<E> *node = new Node<E>(element, prev.next);
            prev.next = node;
        }
        this->m_size++;
    }
    
    E& get(int index) override {
        return nodeAt(index).element;
    }
    
    int indexOf(const E &element) override {
        Node<E> * node = first;
        for (int i = 0; i < this->m_size; i++) {
            if (element == node->element) {
                return i;
            }
            node = node->next;
        }
        return -1;
    }
    
    E& removeAt(int index) override {
        Node<E> *node = first;
        if (index == 0) {
            first = first->next;
        } else {
            Node<E> &prev = this->nodeAt(index - 1);
            node = prev.next;
            prev.next = node->next;
        }
        this->m_size--;
        return node->element;
    }
    
    bool isEmpty() override {
        return this->m_size > 0;
    }
};

单向循环链表

image.png


template<typename E>
class SingleCycleLinkedList: public AbstractList<E> {
private:
    // 获取index位置对应的节点对象
    Node<E> & nodeAt(int index) {
        this->rangeCheck(index);
        Node<E> *node = first;
        for (int i = 0; i < index; i++) {
            node = node->next;
        }
        return *node;
    }
public:
    Node<E> *first { nullptr };
    
    SingleCycleLinkedList() {
        this->m_size = 0;
    }
    
    ~SingleCycleLinkedList() {
        clear();
    }
    
    void clear() override {
        this->m_size = 0;
        if (first != nullptr) {
            Node<E> *node = first->next;
            while (node != nullptr) {
                node = node->next;
                delete node->next;
            }
            delete first;
            first = nullptr;
        }
    }
    
    bool contains(const E &element) override {
        return false;
    }
    
    E& set(int index, const E &element) override {
        Node<E> &node = nodeAt(index);
        E& old = node.element;
        node.element = element;
        return old;
    }
    
    void insert(int index, const E &element) override {
        this->rangeCheckForAdd(index);
        if (index == this->m_size) { // (index == 0 && size == 0) || (index == size && size != 0)
            if (this->m_size == 0) {
                first = new Node<E>(element, nullptr);
                first->next = first;
            } else {
                Node<E> &prev = nodeAt(index - 1);
                Node<E> *node = new Node<E>(element, first);
                prev.next = node;
            }
        } else {
            if (index == 0) {
                Node<E> &last = nodeAt(this->m_size - 1);
                Node<E> *oldFirst = first;
                Node<E> *node = new Node<E>(element, oldFirst);
                last.next = node;
                first = node;
            } else {
                Node<E> &prev = nodeAt(index - 1);
                Node<E> *node = new Node<E>(element, prev.next);
                prev.next = node;
            }
        }
        this->m_size++;
    }
    
    E& removeAt(int index) override {
        this->rangeCheck(index);
        Node<E> *node = first;
        if (index == 0) { // 头部
            Node<E> &oldLast = nodeAt(this->m_size - 1);
            first = first->next;
            oldLast.next = first;
        } else if (index == this->m_size) { // 尾部
            Node<E> &prev = this->nodeAt(index - 1);
            node = prev.next;
            prev.next = first;
        } else {
            Node<E> &prev = this->nodeAt(index - 1);
            node = prev.next;
            prev.next = node->next;
        }
        this->m_size--;
        E &element = node->element;
        delete node;
        return element;
    }
    
    E& get(int index) override {
        return nodeAt(index).element;
    }
    
    int indexOf(const E &element) override {
        Node<E> * node = first;
        for (int i = 0; i < this->m_size; i++) {
            if (element == node->element) {
                return i;
            }
            node = node->next;
        }
        return -1;
    }

    bool isEmpty() override {
        return this->m_size > 0;
    }
    
    void printAll() {
        for (int i = 0; i < this->m_size; i++) {
            Node<E> &node = nodeAt(i);
            cout << node.element << "_" << node.next->element << endl;
        }
    }
};

双向链表

image.png


template <typename E>
class DoubleNode {
public:
    E element;
    DoubleNode<E>* prev { nullptr };
    DoubleNode<E>* next { nullptr };
    
    DoubleNode(E element, DoubleNode<E>* prev, DoubleNode<E>* next) {
        this->element = element;
        this->prev = prev;
        this->next = next;
    }
    
    ~DoubleNode() {
    }
};

template <typename E>
class DoubleLinkedList: public AbstractList<E> {

private:
    // 获取index位置对应的节点对象
    DoubleNode<E> & nodeAt(int index) {
        this->rangeCheck(index);
        if (index < this->m_size >> 1) {
            DoubleNode<E> *node = first;
            for (int i = 0; i < index; i++) {
                node = node->next;
            }
            return *node;
        } else {
            DoubleNode<E> *node = last;
            for (int i = this->m_size - 1; i > index; i--) {
                node = node->prev;
            }
            return *node;
        }
    }
    
public:
    DoubleNode<E> *first { nullptr };
    DoubleNode<E> *last { nullptr };
    
    DoubleLinkedList() {
        this->m_size = 0;
    }
    
    ~DoubleLinkedList() {
        clear();
    }
    
    void clear() override {
        this->m_size = 0;
        if (first != nullptr) {
            DoubleNode<E> *node = first->next;
            while (node != nullptr) {
                node = node->next;
                delete node->next;
            }
            delete first;
            first = nullptr;
        }
    }
    
    bool contains(const E &element) override {
        return false;
    }
    
    E& set(int index, const E &element) override {
        DoubleNode<E> &node = nodeAt(index);
        E& old = node.element;
        node.element = element;
        return old;
    }
    
    void insert(int index, const E &element) override {
        if (this->m_size == 0) { // 链表没得值
            DoubleNode<E> *node = new DoubleNode<E>(element, nullptr, nullptr);
            first = node;
            last = node;
        } else if (index == 0) { // 在头部插入
            DoubleNode<E> *oldFirst = first;
            DoubleNode<E> *node = new DoubleNode<E>(element, nullptr, oldFirst);
            oldFirst->prev = node;
            first = node;
        } else if (index == this->m_size) { // 在尾部插入
            DoubleNode<E> *oldLast = last;
            DoubleNode<E> *node = new DoubleNode<E>(element, oldLast, nullptr);
            oldLast->next = node;
            last = node;
        } else { // 在中间插入
            this->rangeCheckForAdd(index);
            DoubleNode<E> &oldCurrent = nodeAt(index);
            DoubleNode<E> *node = new DoubleNode<E>(element, oldCurrent.prev, &oldCurrent);
            oldCurrent.prev->next = node;
            oldCurrent.prev = node;
        }
        
        this->m_size++;
    }
    
    E& get(int index) override {
        return nodeAt(index).element;
    }
    
    int indexOf(const E &element) override {
        DoubleNode<E> * node = first;
        for (int i = 0; i < this->m_size; i++) {
            if (element == node->element) {
                return i;
            }
            node = node->next;
        }
        return -1;
    }
    
    E& removeAt(int index) override {
        this->rangeCheck(index);
        DoubleNode<E> &node = nodeAt(index);
        if (node.prev == nullptr) {
            DoubleNode<E> *oldFirst = first;
            first = node.next;
            node.next->prev = nullptr;
            delete oldFirst;
        } else if(node.next == nullptr) {
            DoubleNode<E> *oldlast = last;
            last = node.prev;
            node.prev->next = nullptr;
            delete oldlast;
        } else {
            DoubleNode<E> *oldPrev = node.prev;
            DoubleNode<E> *oldnext= node.next;
            node.prev->next = node.next;
            node.next->prev = node.prev;
            delete oldPrev;
            delete oldnext;
            oldPrev = nullptr;
            oldnext = nullptr;
        }
      
        this->m_size--;
        return node.element;
    }
    
    bool isEmpty() override {
        return this->m_size > 0;
    }
};

双向循环链表

接口设计思路与单向循环链表类似

image.png

删除链表中的一个节点

给定单向链表的头指针和一个要删除的节点的值，定义一个函数删除该节点。返回删除后的链表的头节点。
示例 1:
- 输入: head = [4,5,1,9], val = 5
- 输出: [4,1,9]
- 解释: 给定你链表中值为 5 的第二个节点，那么在调用了你的函数之后，该链表应变为 4 -> 1 -> 9.
示例 2:
- 输入: head = [4,5,1,9], val = 1
- 输出: [4,5,9]
- 解释: 给定你链表中值为 1 的第三个节点，那么在调用了你的函数之后，该链表应变为 4 -> 5 -> 9.

    Node<E>* deleteNode(E val) {
        Node<E> * node = first;
        while (node != nullptr && node->next != nullptr) {
            if (node->element == val) {
                return node->next;
            } if (node->next->next == nullptr && node->next->element == val) {
                node->next = nullptr;
                return first;
            } else if (node->next->element == val) {
                node->next = node->next->next;
                return first;
            }
            node = node->next;
        }
        return nullptr;
    }

翻转链表

定义两个指针： prepre 和 curcur ；prepre 在前 curcur 在后。
每次让 prepre 的 nextnext 指向 curcur ，实现一次局部反转
局部反转完成之后， prepre 和 curcur 同时往前移动一个位置
循环上述过程，直至 prepre 到达链表尾部

   Node<E>* reverseList() {
        Node<E> *pre = first;
        Node<E> *cur = nullptr;
        while (pre != nullptr) {
            Node<E> *temp =  pre->next;
            pre->next = cur;
            cur = pre;
            pre = temp;
        }
        return cur;
    }

判断链表是否有环

解题思路
- 采用快慢指针，有环时，快指针和慢指针会指向同一个地址

bool hasCycle() {
        if (first == nullptr || first->next == nullptr) {
            return false;
        }
        Node<E> *slow = first;
        Node<E> *fast = first->next;
        while (fast != nullptr && fast->next != nullptr) {
            if (fast == slow) {
                return true;
            }
            slow = slow->next;
            fast = fast->next->next;
        }
        return false;
    }

链表

线性表是具有 n 个相同类型元素的有限序列（ n ≥ 0 ）

动态数组的缺点

链表

单向链表

单向循环链表

双向链表

双向循环链表

删除链表中的一个节点

翻转链表

判断链表是否有环

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热点阅读

链表

线性表 是具有 n 个相同类型元素 的有限 序列 （ n ≥ 0 ）

动态数组的缺点

链表

单向链表

单向循环链表

双向链表

双向循环链表

删除链表中的一个节点

翻转链表

判断链表是否有环

猜你喜欢

热点阅读

线性表是具有 n 个相同类型元素的有限序列（ n ≥ 0 ）