简单模式匹配/KMP算法

#include<stdio.h>
#define MaxSize 255
typedef struct
{
	char ch[MaxSize];
	int length;
}SString;
void InitStr(SString &S)	
{
	S.ch[0]=' ';
	S.length=0;
}
void StrCreate(SString &S,char a[])	
{
	int i=0,j=1;
	while(a[i]!='\0')
	{
		S.ch[j++]=a[i++];
	}
	S.length=i;
}
int Index(SString S,SString T)		//1.简单模式匹配
{
	int i,k,j;
	k=1;i=k;j=1;
	while(i<S.length && j<T.length)
	{
		if(S.ch[i]==T.ch[j])
		{
			i++;j++;
		}
		else		//匹配失败,主串模式串皆回退重新匹配
		{
			k++;
			i=k;
			j=1;
		}
	}
	if(j>=T.length)
		return k;
	else 
		return 0;
}
void get_next(SString T,int next[])		//模式串右移位数
{
	int i=1,j=0;
	next[1]=0;
	while(i<T.length)
	{
		if(j==0 || T.ch[i]==T.ch[j])
		{
			i++;j++;
			next[i]=j;
		}
		else
			j=next[j];
	}
}
int Index_KMP(SString S,SString T)		//2.KMP算法
{
	int i=1,j=1;
	int next[255];
	get_next(T,next);
	while(i<=S.length && j<=T.length)
	{
		if(j==0 || S.ch[i]==T.ch[j])
		{
			i++;j++;
		}
		else
			j=next[j];	//模式串向后移动
	}
	if(j>T.length)
		return i-T.length;
	else
		return 0;
}
void main()
{
	SString S;
	InitStr(S);
	char a[]="abcdefg";
	char b[]="bcd";
	StrCreate(S,a);
	SString T;
	StrCreate(T,b);
	printf("The T is Num %d in S\n",Index(S,T));
	printf("The T is Num %d in S\n",Index_KMP(S,T));
}