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DSBookCode/BookCode/第3章/3.16-3.19/3.16-3.19.cpp

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+/***链队的基本操作***/
+
+#include<iostream>
+#include<fstream>
+using namespace std;
+
+#define OK 1
+#define ERROR 0
+#define OVERFLOW -2
+typedef char QElemType;
+typedef int Status;
+typedef char SElemType;
+
+//- - - - - 队列的链式存储结构- - - - - 
+typedef struct QNode {
+	QElemType data;
+	struct QNode *next;
+} QNode, *QueuePtr;
+typedef struct {
+	QueuePtr front; //队头指针
+	QueuePtr rear; //队尾指针
+} LinkQueue;
+
+//算法3.16　链队的初始化
+Status InitQueue(LinkQueue &Q) {//构造一个空队列Q
+	Q.front = Q.rear = new QNode; //生成新结点作为头结点，队头和队尾指针指向此结点
+	Q.front->next = NULL; //头结点的指针域置空
+	return OK;
+}
+
+//算法3.17　链队的入队
+Status EnQueue(LinkQueue &Q, QElemType e) {//插入元素e为Q的新的队尾元素
+	QueuePtr p;
+	p = new QNode; //为入队元素分配结点空间，用指针p指向
+	p->data = e; //将新结点数据域置为e
+	p->next = NULL;
+	Q.rear->next = p; //将新结点插入到队尾
+	Q.rear = p; //修改队尾指针
+	return OK;
+}
+
+//算法3.18　链队的出队
+Status DeQueue(LinkQueue &Q, QElemType &e) {//删除Q的队头元素，用e返回其值 
+	QueuePtr p;
+	if (Q.front == Q.rear)
+		return ERROR; //若队列空，则返回ERROR
+	p = Q.front->next; //p指向队头元素
+	e = p->data; //e保存队头元素的值
+	Q.front->next = p->next; //修改头指针
+	if (Q.rear == p)
+		Q.rear = Q.front; //最后一个元素被删，队尾指针指向头结点
+	delete p; //释放原队头元素的空间
+	return OK;
+}
+
+//算法3.19　取链队的队头元素
+SElemType GetHead(LinkQueue Q) {//返回Q的队头元素，不修改队头指针
+	if (Q.front != Q.rear) //队列非空
+		return Q.front->next->data; //返回队头元素的值，队头指针不变
+}
+
+int main() {
+	int choose, flag = 0;
+	LinkQueue Q;
+	QElemType e, j;
+	cout << "1.初始化\n";
+	cout << "2.入队\n";
+	cout << "3.读队头元素\n";
+	cout << "4.出队\n";
+	cout << "0.退出\n\n";
+
+	choose = -1;
+	while (choose != 0) {
+		cout << "请选择:";
+		cin >> choose;
+		switch (choose) {
+		case 1://算法3.16　链队的初始化
+			if (InitQueue(Q)) {
+				flag = 1;
+				cout << "成功对队列进行初始化\n\n";
+			} else
+				cout << "初始化队列失败\n\n";
+			break;
+		case 2: {//算法3.17　链队的入队
+			fstream file;
+			file.open("QNode.txt");
+			if (!file) {
+				cout << "错误！未找到文件！\n\n" << endl;
+				exit(ERROR);
+			}
+			if (flag) {
+				flag = 1;
+				cout << "入队的元素依次为：\n";
+				while (!file.eof()) {
+					file >> j;
+					if (file.fail())
+						break;
+					else {
+						EnQueue(Q, j);
+						cout << j << "  ";
+					}
+				}
+				cout << endl << endl;
+			} else
+				cout << "队列未建立，请重新选择\n\n";
+			file.close();
+		}
+			break;
+		case 3://算法3.19　取链队的队头元素
+			if (flag != -1 && flag != 0)
+				cout << "队头元素为：\n" << GetHead(Q) << endl << endl;
+			else
+				cout << "队列中无元素，请重新选择\n" << endl;
+			break;
+		case 4://算法3.18　链队的出队
+			cout << "依次弹出的队头元素为:\n";
+			while (DeQueue(Q, e)) {
+				flag = -1;
+				cout << e << "  ";
+			}
+			cout << endl << endl;
+			break;
+		}
+	}
+	return 0;
+}

DSBookCode/BookCode/第3章/3.16-3.19/QNode.txt

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+A
+B
+C
+D