delete.cpp

学校的教学管理系统

#include"head.h"
#include<iostream.h>
#include<stdlib.h>
#include<string.h>

void DeleteStudent(Student* &head)
{
	Student* pGuard;
	Student* p;
	char Name[20];
	char choice;
	int Class;
	int Number;
	pGuard=head;

	cout<<"说明:"<<endl
		<<"本程序提供①按照学生学号"<<endl
		<<"          ②按照学生所在班级和姓名"<<endl
		<<"          两种方式来删除一个学生的信息."
		<<endl;
	cout<<"请选择删除方式(1/2):";
	cin>>choice;

	system("cls");

	if(choice=='1')
	{
status1:
		cout<<"请输入要删除的学生学号:";
		cin>>Number;
		if(head->Number==Number)
		{
			head=pGuard->next;
			delete pGuard;
			cout<<"删除成功!"<<endl;
			return;
		}
		for(pGuard=head;pGuard->next!=NULL;pGuard=pGuard->next)
		{
			if(pGuard->next->Number==Number)
			{
				p=pGuard->next;
				pGuard->next=p->next;
				delete p;
				cout<<"删除成功!"<<endl;
				return;
			}
		}
status2:
		cout<<"没有找到您输入的学生学号,删除失败."<<endl;
		cout<<"要重新输入吗?(y/n)";
		cin>>choice;
				
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status1;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您键入的内容有误,请重新选择."<<endl;
			goto status2;
		}
	}

	else if(choice=='2')
	{
status3:
		cout<<"请输入要删除的学生的班级:"<<endl;
		cin>>Class;
		cout<<"请输入要删除的学生的姓名:";
		cin>>Name;

		if(head->Class==Class&&strcmp(head->Name,Name)==0)
		{
			head=pGuard->next;
			delete pGuard;
			cout<<"删除成功!"<<endl;
			return;
		}
		for(pGuard=head;pGuard->next!=NULL;pGuard=pGuard->next)
		{
			if(pGuard->next->Class==Class&&strcmp(pGuard->next->Name,Name)==0)
			{
				p=pGuard->next;
				pGuard->next=p->next;
				delete p;
				cout<<"删除成功!"<<endl;
				return;
			}
		}
status4:
		cout<<"没有找到您输入的学生,删除失败."<<endl;
		cout<<"要重新输入吗?(y/n)";
		cin>>choice;
				
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status3;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您键入的内容有误,请重新选择."<<endl;
			goto status4;
		}
	}
		
}


void DeleteClass(Student* &head)
{
	Student* left;
	Student* right;
	Student* p;
	char choice;
	int Class;
	left=head;

status5:
	cout<<"请输入您要删除的班级:";
	cin>>Class;

	if(head->Class==Class)
	{
		for(right=head;right->next!=NULL;right=right->next)
		{
			if(right->next->Class!=Class)
			{
				break;
			}
		}
		
		head=right->next;        //改变head的指向

		while(left!=right)		 //以下一段删除left和right之间的所有节点
		{
			p=left;
			left=left->next;
			delete p;
		}
		delete left;            //这里因为left=right,也可以用 "delete right;"
		
		cout<<"删除成功!"<<endl;
		return;
	}
	for(left=head;left->next!=NULL;left=left->next)  //左指针定位
	{
		if(left->next->Class==Class)    //there used to be an error here!!!!
		{
			break;
		}
	}
		
	if(left->next==NULL)       //如果左指针没有定位,那么右指针也不用定位了
	{
status6:
		cout<<"没有找到您输入的班级,删除失败."<<endl;
		cout<<"要重新输入吗?(y/n):";
		cin>>choice;
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status5;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您键入的内容有误,请重新选择."<<endl;
			goto status6;
		}
	}
		
	for(right=left;right->next!=NULL;right=right->next)  //右指针定位
	{
		if(right->next->Class!=Class)
		{
			break;
		}
	}

	for(p=head;p->next !=left;p=p->next)  //改变left前一节点中next的指向
		;
	p->next=right->next;

	while(left!=right)              //和上面一样,删除left和right之间的所有节点
	{
		p=left;
		left=left->next;
		delete p;
	}
	delete left;

	cout<<"删除成功!"<<endl;
}


void DeleteAll(Student* &head)         //释放动态分配的内存
{
	Student *pGuard;
	Student *p;
	p=pGuard=head;

	while(p!=NULL)
	{
		pGuard=pGuard->next;
		delete p;
		p=pGuard;
	}
}