C++數據結構：單鏈表、雙鏈表與循環鏈表

注意：以下所有鏈表均包含空的頭結點。

1 單鏈表（SingleLinkedList）

1.1 代碼

#include "stdafx.h"
#include <iostream>

using namespace std;

//節點類
class Node {
public:
	int data;
	Node * next;

	//兩個參數的構造函數
	Node(const int info, Node * nextValue) {
		data = info;
		next = nextValue;
	}

	//一個參數的構造函數
	Node(Node * nextValue) {
		next = nextValue;
	}
};

//單鏈表類
class SingleLinkedList {
private:
	Node *head, *tail;

	//返回線性表指向第p個元素的[指針值]
	Node *setPos(const int i) {
		int count = 0;
		if (i == -1) {
			return head;
		}
		Node *p = new Node(head->next);
		while (p != NULL && count < i) {
			p = p->next;
			count++;
		}
		return p;
	}

public:
	SingleLinkedList() {
		head = tail = new Node(NULL);
	}

	~SingleLinkedList() {
		Node *tmp;
		while (head != NULL) {
			tmp = head;
			head = head->next;
			delete tmp;
		}
	}

	//判斷鏈表是否爲空
	bool isEmpty() {
		if (head->next == NULL)
			return true;
		else
			return false;
	}

	//將鏈表內容清除
	void clear() {
		Node *tmp;
		while (head != NULL) {
			tmp = head;
			head = head->next;
			delete tmp;
		}
		head = tail = new Node(NULL);
	}

	//返回當前鏈表長度
	int length() {
		int count = 0;
		Node *p = new Node(head->next);
		while (p != NULL) {
			p = p->next;
			count++;
		}
		return count;
	}

	//在表尾添加一元素
	bool append(const int value) {
		Node *p = new Node(value, tail->next);
		tail->next = p;
		tail = p;	//tail重置
		return true;
	}

	//在位置i上插入一個元素value
	bool insert(const int i, const int value) {
		Node *p, *q;
		if ((p = setPos(i - 1)) == NULL) {
			cout << "Illegle location of insertion!" << endl;
			return false;
		}
		q = new Node(value, p->next);	//q是待插入元素
		p->next = q;
		if (p == tail)	//插入點在鏈尾
			tail = q;
		return true;
	}

	//在位置i上刪除該元素
	bool drop(const int i) {
		Node *p, *q;
		if ((p = setPos(i - 1)) == NULL || p == tail) {
			cout << "Illegle location of delete operation!" << endl;
			return false;
		}
		q = p->next;	//q是待刪除元素
		if (q == tail) {
			tail = p;
			p->next = NULL;
			delete q;
		}
		else if (q != NULL) {
			p->next = q->next;
			delete q;
		}
	}

	//通過value返回位置p的元素值
	bool getValue(const int p, int & value) {
		if (p == -1) {
			value = NULL;
			return false;
		}
		Node *q = head;
		for (int i = 0; i < p; i++) {
			q = q->next;
		}
		value = q->data;
		return true;
	}

	//查找值爲value的元素並通過p返回其第一次出現時的位置
	bool getPos(int &p, const int value) {
		Node *q;
		p = 0;
		for (q = head; q != NULL; q = q->next, ++p) {
			if (q->data == value) {
				return true;
				break;
			}
		}
		return false;
	}
};

1.2 測試

int main()
{
	SingleLinkedList test;
	int tmp;

	if (test.isEmpty())
		cout << "Empty linked list." << endl;
	else
		cout << "Linked list is Not Empty." << endl;
	cout << "Length: " << test.length() << endl;	//空表頭，長度一開始就是1
	test.append(1);
	test.append(2);
	test.append(3);
	test.getValue(0, tmp);
	cout << "Value: " << tmp << endl;
	test.getValue(1, tmp);
	cout << "Value: " << tmp << endl;
	test.getValue(2, tmp);
	cout << "Value: " << tmp << endl;
	test.getValue(3, tmp);
	cout << "Value: " << tmp << endl;
	if (test.isEmpty())
		cout << "Empty linked list." << endl;
	else
		cout << "Linked list is Not Empty." << endl;
	cout << "Length: " << test.length() << endl;
	test.insert(2, 4);
	test.getPos(tmp, 4);
	cout << "Positon: " << tmp << endl;
	test.getValue(2, tmp);
	cout << "Value: " << tmp << endl;
	test.drop(2);
	return 0;
}

1.3 輸出

Empty linked list.
Length: 1
Value: 0
Value: 1
Value: 2
Value: 3
Linked list is Not Empty.
Length: 4
Positon: 2
Value: 4

2 雙鏈表（DoubleLinkedList）

這部分代碼相較於1.1節的內容修改不大，主要變化體現在insert()和drop()方法內部以及類DoubleLinkedList中函數的形參變化上。
測試用例和輸出結果同1.2和1.3節，故省略。

#include "stdafx.h"
#include <iostream>

using namespace std;

//節點類
class Node {
public:
	int data;
	Node * next;
	Node * prev;

	//包含值和前後指針三個參數的構造函數
	Node(const int info, Node * preValue, Node * nextValue) {
		data = info;
		prev = preValue;
		next = nextValue;
	}

	//包含前後指針兩個參數的構造函數
	Node(Node * preValue, Node * nextValue) {
		prev = preValue;
		next = nextValue;
	}
};

//雙鏈表類
class DoubleLinkedList {
private:
	Node *head, *tail;

	//返回線性表指向第p個元素的[指針值]
	Node *setPos(const int i) {
		int count = 0;
		if (i == -1) {
			return head;
		}
		Node *p = new Node(head, head->next);
		while (p != NULL && count < i) {
			p = p->next;
			count++;
		}
		return p;
	}

public:
	DoubleLinkedList() {
		head = tail = new Node(NULL, NULL);
	}

	~DoubleLinkedList() {
		Node *tmp;
		while (head != NULL) {
			tmp = head;
			head = head->next;
			delete tmp;
		}
	}

	//判斷鏈表是否爲空
	bool isEmpty() {
		if (head->next == NULL)
			return true;
		else
			return false;
	}

	//將鏈表內容清除
	void clear() {
		Node *tmp;
		while (head != NULL) {
			tmp = head;
			head = head->next;
			delete tmp;
		}
		head = tail = new Node(NULL, NULL);
	}

	//返回當前鏈表長度
	int length() {
		int count = 0;
		Node *p = new Node(head, head->next);
		while (p != NULL) {
			p = p->next;
			count++;
		}
		return count;
	}

	//在表尾添加一元素
	bool append(const int value) {
		Node *p = new Node(value, tail, tail->next);
		tail->next = p;
		tail = p;	//tail重置
		return true;
	}

	//在位置i上插入一個元素value
	bool insert(const int i, const int value) {
		Node *p, *q;
		if ((p = setPos(i - 1)) == NULL) {
			cout << "Illegle location of insertion!" << endl;
			return false;
		}
		q = new Node(value, p, p->next);	//q是待插入元素
		q->prev = p;
		q->next = p->next;
		p->next = q;
		q->prev->next = q;
		if (p == tail)	//插入點在鏈尾
			q = tail;
		return true;
	}

	//在位置i上刪除該元素
	bool drop(const int i) {
		Node *p;		//p本身就是待刪除元素
		if ((p = setPos(i - 1)) == NULL || p == tail) {
			cout << "Illegle location of delete operation!" << endl;
			return false;
		}
		if (p == tail) {
			tail = p->prev;
			p->prev->next = NULL;
			delete p;
		}
		else if (p != NULL) {
			p->prev->next = p->next;
			p->next->prev = p->prev;
			p->prev = NULL;
			p->next = NULL;
			delete p;
		}
	}

	//通過value返回位置p的元素值
	bool getValue(const int p, int & value) {
		if (p == -1) {
			value = NULL;
			return false;
		}
		Node *q = head;
		for (int i = 0; i < p; i++) {
			q = q->next;
		}
		value = q->data;
		return true;
	}

	//查找值爲value的元素並通過p返回其第一次出現時的位置
	bool getPos(int &p, const int value) {
		Node *q;
		p = 0;
		for (q = head; q != NULL; q = q->next, ++p) {
			if (q->data == value) {
				return true;
				break;
			}
		}
		return false;
	}
};