数据结构_串_用链表做存储结构实现KMP算法_C++实现

      写这个纠结了很久，老是会有某个环节出问题。先是在处理串的结束标志的问题上，老是会跟其他的判断条件冲突造成提前退出，而且无论主串和模式串情况如何结果总是succeed，尝试了好几种方法，包括将其链接成单循环链表等，效果总是不太理想，后来就想到了临时new一个变量，用完之后再delete掉，结果由于多写了一个delete老是报错，后来才发现在ReMove函数中已经delete掉了。然后就是GetNext()和KMP()处理上有点小问题，有一些细节没有处理好。后来在纸上做了下模拟，也慢慢调过来了，贴出来分享一下，如有错误，欢迎指正。

"head.h"

#include<iostream>
using namespace std;

class NODE
{
public:
	NODE();
	char ch;
	NODE * succ;//指向下一个节点
	NODE * next;//对于主串指向前一个节点；对于模式串指向"失配"下一个要进行比较的节点
};

NODE::NODE()
{
	succ=next=NULL;
}


class STRING
{
public:
	STRING();
	void GetMainString();
	void GetSubstring();
	void KMP();
	void Print();
private:
	void GetNext();
	void ReMove(NODE *);
	void GetLeftString(NODE *);
	NODE *head1,*p1,*end1,*head2,*p2,*end2;
	//end1标示主串的结尾end2标示模式串的结尾
};

STRING::STRING()
{
	end1=head1=p1=end2=head2=p2=NULL;
}

void STRING::GetMainString()//得到主串
{
	cout<<"GetMainString Called !"<<endl<<endl;
	char ch;
	if(head1!=NULL)//释放节点内存
	{
		ReMove(head1);
		head1=NULL;
//		delete end1;
		//注意这里不用释放end1的内存，因为在ReMove中结束条件是p==NULL，已经把end1的内存给释放掉了
	}
	while(cin>>ch)
	{
		if(head1==NULL)
		{
			head1=new NODE;
			head1->ch=ch;
			head1->next=head1;
			p1=head1;
		}
		else
		{
			p1->succ=new NODE;
			p1->succ->ch=ch;
			p1->succ->next=p1;
			p1=p1->succ;
		}
	}
	if(head1!=NULL)
	{
		p1->succ=end1=new NODE;//给串尾添加结束标志
	}
	cin.clear();
}

void STRING::GetSubstring()//得到模式串
{
	cout<<"GetSubString Called !"<<endl<<endl;
	char ch;
	if(head2!=NULL)
	{
		ReMove(head2);
		head2=NULL;
//		delete end2;
	}
	while(cin>>ch)
	{
		if(head2==NULL)
		{
			head2=new NODE;
			head2->ch=ch;
			p2=head2;
		}
		else
		{
			p2->succ=new NODE;
			p2=p2->succ;
			p2->ch=ch;
		}
	}
	if(head2!=NULL)
	{
		p2->succ=end2=new NODE;
	}
	cin.clear();
}
 
void STRING::KMP()//KMP算法核心
{
	cout<<"KMP Called !"<<endl<<endl;
	if(head1==NULL||head2==NULL)//空串处理
	{
		cout<<"Failed !"<<endl<<endl;
	}
	GetNext();//得到next"值"
	p1=head1;
	p2=head2;
	while(p1!=end1&&p2!=end2)
	{
		if(p2==NULL||p1->ch==p2->ch)
		{
			p1=p1->succ;
			if(p2==NULL)
				p2=head2;
			else
				p2=p2->succ;
		}
		else
		{
			p2=p2->next;
		}
	}
	if(p2==end2)//判断是否匹配成功
	{
		cout<<"Succeed ! The Left Of The String is = ";
		GetLeftString(p1);
	}
	else
	{
		cout<<"Failed !"<<endl<<endl;
	}
}

void STRING::Print()//输出主串和模式串的内容
{
	cout<<"Print Called !"<<endl<<endl;
	if(head1==NULL)
	{
		cout<<"No Data In MainString !"<<endl<<endl;
	}
	else
	{
		cout<<"MainString = ";
		p1=head1;
		while(p1!=end1)
		{
			cout<<p1->ch;
			p1=p1->succ;
		}
		cout<<endl<<endl;
	}
	if(head2==NULL)
	{
		cout<<"No Data In SubString !"<<endl<<endl;
	}
	else
	{
		cout<<"SubString = ";
		p2=head2;
		while(p2!=NULL)
		{
			cout<<p2->ch;
			p2=p2->succ;
		}
		cout<<endl<<endl;
	}
}
 
void STRING::GetNext()//得到模式串的next值
{
	p1=head2;
	p2=head2->next=NULL;
	while(p1->succ!=end2)
	{
		if(p2==NULL||p1->ch==p2->ch)
		{
			p1=p1->succ;
			if(p2==NULL)
				p2=head2;
			else
				p2=p2->succ;
			if(p2!=p2->next)
				p1->next=p2;
			else
				p2=p2->next;
		}
		else
		{
			p2=p2->next;
		}
	}
}

void STRING::GetLeftString(NODE *p)//输出匹配成功后主串中剩下的部分
{
	while(p!=end1)
	{
		cout<<p->ch;
		p=p->succ;
	}
	cout<<endl<<endl;
}

void STRING::ReMove(NODE *p)//销毁字符串所占的内存
{
	if(p==NULL)
		return;
	else
	{
		ReMove(p->succ);
		delete p;
	}
}

"main.cpp"

#include<iostream>
#include"head.h"
using namespace std;

int main()
{
	char choice;
	STRING str;
	while(1)
	{
		cout<<"Your Choice Please ?"<<endl<<endl
			<<"1 . SetMainString"<<endl
			<<"2 . SetSubString"<<endl
			<<"3 . KMP"<<endl
			<<"4 . Print"<<endl
			<<"5 . Quit"<<endl<<endl;
		cin>>choice;
		system("cls");
		switch(choice)
		{
		case '1':
			str.GetMainString();
			break;
		case '2':
			str.GetSubstring();
			break;
		case '3':
			str.KMP();
			cin.get();
			cin.get();
			break;
		case '4':
			str.Print();
			cin.get();
			cin.get();
			break;
		case '5':
			return 0;
			break;
		default:
			cout<<"No Such Choice !"<<endl<<endl;
			cin.get();
			cin.get();
			break;
		}
		system("cls");
	}

}