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