依照KMP實現的算法，附帶測試用例。

#include <algorithm>
#include<iostream>
#include<iterator>
#include <string>
#include <vector>
#include <cassert>
#include <cstring>
using namespace std;


/**計算next***/
void kmp_next(char *pattern,int *next)
{
int i = 0 ;
int j = next[0] = -1;
while(pattern[i]!= '\0')
{
if((j == -1) || (pattern[i] == pattern[j]))
next[++i]= ++j;
else
j = next[j];
}
}
/**計算next_val***/
void kmp_next_val(char *pattern,int *next_val)
{
int i = 0;
int j = next_val[0] = -1;
while(pattern[i]!='\0')
{
if((j == -1)|| (pattern[i] == pattern[j]))
if(pattern[++i] != pattern[++j])
next_val[i] = j;
else
next_val[i] = next_val[j];
else
j = next_val[j];
}
}
/****match 是長串**

*****pattern 是模式串**/
int kmp_match(char *match,char *pattern)
{
int m = strlen(pattern);

int next[m];
int i,j;
/**打印表格**/
for(i = 0; i < m ; ++i)
cout<<i<<'\t';
cout<<endl;
kmp_next(pattern,next);
copy(next,next+m,ostream_iterator<int > (cout,"\t"));
cout<<endl;
kmp_next_val(pattern,next);
copy(next,next+m,ostream_iterator<int > (cout,"\t"));
cout<<endl;

i = j = 0;
while((match[i]!='\0')&&(pattern[j]!='\0'))
{
if((j == -1)||(match[i] == pattern[j]))
++i,++j;
else
j = next[j];

}
return j == m?(i -j):-1;
}


int main(int argc,char *argv[])
{
char src[max_size];
char dst[max_size];
int m ,n;
int position = 0;
while(cin >> src >> dst)
{
position = kmp_match(src,dst);

if(position != -1)
cout<<"find at \t "<<position<<endl;
else
cout<<"not a substring\n";

cout<<"--------end----------\n\n";
}
return 0;
}

轉載于:https://www.cnblogs.com/westfly/archive/2011/05/04/kmp_algorithm.html

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