Soundex() Function in C/C++

Posted on 2001-06-29
Last Modified: 2008-01-09
looking for source code listing in C/C++ that returns a phonetic representation of a specified Character expresssion.
Question by:Loysi
LVL 14

Expert Comment

ID: 6240302
soundex resources and soundex code of Bob Stout
same thing (mirror)
files Phonetic.H,Soundex4.C,Soundex5.C,Metaphon.C,Approx.C

Accepted Solution

smnaha earned 50 total points
ID: 6240398
Hi Alex,

This is the soundex algorithm implementation which I use. You might want to validate the input data more rigorously than what it is here. It is an implementation of the algorithm described in Knuth's The Art of Computer Programming, Volume 3.

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

const  int CODE_LEN = 4;

static char soundnum[26] = {
     '0', '1', '2', '3', '0', '1', '2', 'h', '0','2',
     '2', '4', '5', '5', '0', '1', '2', '6', '2','3',
     '0', '1', 'w', '2', '0', '2'};

int compact (char *s, int nsize)
     int i = 0, j = 0;
     for (i=1, j=1; i < nsize; ++i) {
          if (s[i] != s[i-1]) {    
               s[j] = s[i];
     s[j] = '\0';
     return j;

/* soundex code for a string is always 4 characters in length */
/* this soundex code is the implementation of the soundex */
/* algorithm described in "The Art of Computer Programming, Vol 3, */
/* Sorting and Searching, by Donald E. Knuth */
int __stdcall GetSoundCode (const char *szString, char *szCode)
     char *cp;
     char *stemp ;
     char *s = 0;
     int len = 0;

     if (szCode == 0) {
          return 0;

     len = strlen(szCode);
     if (len < CODE_LEN)
          return 0;

     stemp = (char*)malloc(strlen(szString) * sizeof(char));
     if (stemp == 0)
          return 0;

     strcpy (stemp, szString);

     s = stemp;
     while (*s) {
          *s = soundnum[*s - 'a'];
          if (*s == 'h' || *s == 'w')
               *s = *(s-1);
     compact (stemp, strlen(stemp));
     szCode[0] = szCode[1] = szCode[2] = szCode[3] = '0';
     szCode[4] = '\0';
     cp = szCode;
     s = stemp;
     while (*s && *cp) {
          if (*s != '0') {
               *cp = *s;

     return 1;

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