kmp算法

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kmp 模式匹配

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#include <iostream>
#include<string.h>
int n,m;
int prefix[100];
using namespace std;
void prefix_table(char patt[],int n){
	prefix[0]=0;
	int i=1;
	int len=0;
	while(i<n){
		
		if(patt[i]==patt[len])
		{
			len++;
			prefix[i]=len;
			i++;
		}
		else{
			if(len>0)
			len=prefix[len-1];
			else{
				prefix[i]=len;
				i++;
			}
		}
	}
}
void move_prefix(int prefix[],int n){
	for(int i=n-1;i>0;i--) prefix[i]=prefix[i-1];
	prefix[0]=-1;
}
void kmp(char txt[],char patt[]){
	

	prefix_table(patt,n);
	move_prefix(prefix,n);
	int i=0,j=0;
	m=strlen(txt);

	while(i<m){
		if(j==n-1&&txt[i]==patt[j])//!!
		{
		//	cout<<i<<endl;
		//	cout<<j<<endl;
			cout<<"Found at:"<<i-j<<endl;
			j=prefix[j];
	//	cout<<"j:"<<j;
		}
		if(txt[i]==patt[j]){
			i++;j++;
		}
		else{
			j=prefix[j];
			if(j==-1){
				i++;
				j++;
			}
		}
	}
}
int main(){
	char patt[100];
	strcpy(patt,"BABA");
	n=strlen(patt); 
	char txt[100];
	strcpy(txt,"ABABABA");
	kmp(txt,patt);
}

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