# LevenshteinXS.xs   [plain text]

```#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

/****************************************************/
/* Levenshtein Distance Algorithm		    */
/* C Implementation by Lorenzo Seidenari	    */
/* http://www.merriampark.com/ldc.htm		    */
/* modified by dree				    */
/****************************************************/

#include <stdlib.h>
#include <string.h>

int levenshtein_distance(char *s,char*t);
int minimum(int a,int b,int c);

int levenshtein_distance(char *s,char*t)

/*Compute levenshtein distance between s and t*/
{
//Step 1
int k,i,j,n,m,cost,*d,distance;
if (strcmp(s,t) == 0) {return 0;}
n=strlen(s);
m=strlen(t);
if(n==0) {return m;}
if(m==0) {return n;}

d=malloc((sizeof(int))*(m+1)*(n+1));
m++;
n++;
//Step 2
for(k=0;k<n;k++)
d[k]=k;
for(k=0;k<m;k++)
d[k*n]=k;
//Step 3 and 4
for(i=1;i<n;i++)
for(j=1;j<m;j++)
{
//Step 5
if(s[i-1]==t[j-1])
cost=0;
else
cost=1;
//Step 6
d[j*n+i]=minimum(d[(j-1)*n+i]+1,d[j*n+i-1]+1,d[(j-1)*n+i-1]+cost);
}
distance=d[n*m-1];
free(d);
return distance;
}

int minimum(int a,int b,int c)
/*Gets the minimum of three values*/
{
int min=a;
if(b<min)
min=b;
if(c<min)
min=c;
return min;
}

MODULE = Text::LevenshteinXS		PACKAGE = Text::LevenshteinXS

int
distance(s,t)
char * s
char * t
CODE:
RETVAL = levenshtein_distance(s,t);
OUTPUT:
RETVAL

```