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Levenshtein string distance

master
parent
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abb1d5cb1b
  1. 54
      src/strings/levenshtein.c
  2. 4
      src/strings/levenshtein.h
  3. 32
      testing/test.c

54
src/strings/levenshtein.c

@ -0,0 +1,54 @@
#include "levenshtein.h"
int _min(int a, int b) {
if (a < b) {
return a;
}
return b;
}
// Calculates Levenshtein distance for str1 and str2 of length len1 and len2 respectively
int levenshtein_distance(const char* str1, const char* str2) {
unsigned int len1 = strlen(str1) + 1;
unsigned int len2 = strlen(str2) + 1;
if (len1 == 0) {
return len2;
}
if (len2 == 0) {
return len1;
}
if (strcmp(str1, str2) == 0) {
return 0;
}
char s1[len2];
char s2[len2];
char row[len1];
strcpy(s1, str1);
strcpy(s2, str2);
for (unsigned int i = 0; i < len1; i++) {
row[i] = i;
}
for (unsigned int i = 1; i < len2; i++) {
int previous = i;
for (unsigned int j = 1; j < len1; j++) {
int current = row[j-1];
if (s2[i-1] != s1[j-1]) {
current = _min(_min(row[j-1]+1, previous+1), row[j]+1);
}
row[j-1] = previous;
previous = current;
}
row[len1] = previous;
}
return row[len1];
}

4
src/strings/levenshtein.h

@ -0,0 +1,4 @@
#include <string.h>
// Calculates Levenshtein distance for str1 and str2
int levenshtein_distance(const char* str1, const char* str2);

32
testing/test.c

@ -26,6 +26,7 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
#include "../src/math/vector.h"
#include "../src/math/misc.h"
#include "../src/datastruct/cvec.h"
#include "../src/strings/levenshtein.h"
int test_rng() {
lcg(76);
@ -302,6 +303,29 @@ int test_datastruct() {
return EXIT_SUCCESS;
}
int test_levenshtein() {
const char* str1 = "Fellow";
const char* str2 = "Fella";
int distance = levenshtein_distance(str1, str2);
if (distance != 2) {
printf("[ERROR] Invalid string distance between \"%s\" and \"%s\": expected to be %d; got %d\n", str1, str2, 2, distance);
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
int test_strings() {
if (test_levenshtein() == EXIT_FAILURE) {
printf("[ERROR] Levenshtein test failed\n");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
int main() {
// rng
printf("[INFO] Testing rng...\n");
@ -359,5 +383,13 @@ int main() {
printf("[INFO] Datastruct test passed\n\n");
}
// strings
printf("[INFO] Testing strings...\n");
if (test_strings() == EXIT_FAILURE) {
printf("[INFO] Strings test failed\n\n");
} else {
printf("[INFO] Strings test passed\n\n");
}
return EXIT_SUCCESS;
}
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