#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<<"說明:"<<endl
		<<"本程序提供①按照學生學號"<<endl
		<<"          ②按照學生所在班級和姓名"<<endl
		<<"          兩種方式來刪除一個學生的信息."
		<<endl;
	cout<<"請選擇刪除方式(1/2):";
	cin>>choice;

	system("cls");

	if(choice=='1')
	{
status1:
		cout<<"請輸入要刪除的學生學號:";
		cin>>Number;
		if(head->Number==Number)
		{
			head=pGuard->next;
			delete pGuard;
			cout<<"刪除成功!"<<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<<"刪除成功!"<<endl;
				return;
			}
		}
status2:
		cout<<"沒有找到您輸入的學生學號,刪除失敗."<<endl;
		cout<<"要重新輸入嗎?(y/n)";
		cin>>choice;
				
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status1;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您鍵入的內容有誤,請重新選擇."<<endl;
			goto status2;
		}
	}

	else if(choice=='2')
	{
status3:
		cout<<"請輸入要刪除的學生的班級:"<<endl;
		cin>>Class;
		cout<<"請輸入要刪除的學生的姓名:";
		cin>>Name;

		if(head->Class==Class&&strcmp(head->Name,Name)==0)
		{
			head=pGuard->next;
			delete pGuard;
			cout<<"刪除成功!"<<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<<"刪除成功!"<<endl;
				return;
			}
		}
status4:
		cout<<"沒有找到您輸入的學生,刪除失敗."<<endl;
		cout<<"要重新輸入嗎?(y/n)";
		cin>>choice;
				
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status3;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您鍵入的內容有誤,請重新選擇."<<endl;
			goto status4;
		}
	}
		
}


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

status5:
	cout<<"請輸入您要刪除的班級:";
	cin>>Class;

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

		while(left!=right)		 //以下一段刪除left和right之間的所有節(jié)點
		{
			p=left;
			left=left->next;
			delete p;
		}
		delete left;            //這里因為left=right,也可以用 "delete right;"
		
		cout<<"刪除成功!"<<endl;
		return;
	}
	for(left=head;left->next!=NULL;left=left->next)  //左指針定位
	{
		if(left->next->Class==Class)    //there used to be an error here!!!!
		{
			break;
		}
	}
		
	if(left->next==NULL)       //如果左指針沒有定位,那么右指針也不用定位了
	{
status6:
		cout<<"沒有找到您輸入的班級,刪除失敗."<<endl;
		cout<<"要重新輸入嗎?(y/n):";
		cin>>choice;
		if(choice=='y'||choice=='Y')
		{
			system("cls");
			goto status5;
		}
		else if(choice!='y'&&choice!='Y'&&choice!='n'&&choice!='N')
		{
			cout<<"您鍵入的內容有誤,請重新選擇."<<endl;
			goto status6;
		}
	}
		
	for(right=left;right->next!=NULL;right=right->next)  //右指針定位
	{
		if(right->next->Class!=Class)
		{
			break;
		}
	}

	for(p=head;p->next !=left;p=p->next)  //改變left前一節(jié)點中next的指向
		;
	p->next=right->next;

	while(left!=right)              //和上面一樣,刪除left和right之間的所有節(jié)點
	{
		p=left;
		left=left->next;
		delete p;
	}
	delete left;

	cout<<"刪除成功!"<<endl;
}


void DeleteAll(Student* &head)         //釋放動態(tài)分配的內存
{
	Student *pGuard;
	Student *p;
	p=pGuard=head;

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