[similarity] adding a string array version of Jaccard similarity that creates the string sets internally for convenience

src/jaccard.c

@@ -1,8 +1,7 @@
 #include "jaccard.h"
 
-
 double jaccard_similarity(khash_t(str_set) *s1, khash_t(str_set) *s2) {
-    if (s1 == NULL || s2 == NULL) return -1.0;
+    if (s1 == NULL || s2 == NULL) return 0.0;
 
     size_t set_intersection = 0;
     size_t set_union = 0;
@@ -24,4 +23,47 @@ double jaccard_similarity(khash_t(str_set) *s1, khash_t(str_set) *s2) {
     set_union += kh_size(s2);
 
     return (double)set_intersection / set_union;
-}
+}
+
+
+double jaccard_similarity_string_arrays(size_t num_strings1, char **strings1, size_t num_strings2, char **strings2) {
+    if (strings1 == NULL || strings2 == NULL || num_strings1 == 0 || num_strings2 == 0) return 0.0;
+
+    khash_t(str_set) *string_set1 = kh_init(str_set);
+    if (string_set1 == NULL) return 0.0;
+
+    kh_resize(str_set, string_set1, num_strings1);
+    int ret = 0;
+
+    khiter_t k;
+
+    for (size_t i = 0; i < num_strings1; i++) {
+        char *str1 = strings1[i];
+        k = kh_put(str_set, string_set1, str1, &ret);
+        if (ret < 0) {
+            kh_destroy(str_set, string_set1);
+            return 0.0;
+        }
+    }
+
+    khash_t(str_set) *string_set2 = kh_init(str_set);
+    if (string_set2 == NULL) {
+        kh_destroy(str_set, string_set1);
+        return 0.0;
+    }
+    kh_resize(str_set, string_set2, num_strings2);
+    for (size_t i = 0; i < num_strings2; i++) {
+        char *str2 = strings2[i];
+        k = kh_put(str_set, string_set2, str2, &ret);
+        if (ret < 0) {
+            kh_destroy(str_set, string_set1);
+            kh_destroy(str_set, string_set2);
+            return 0.0;
+        }
+    }
+
+    double sim = jaccard_similarity(string_set1, string_set2);
+    kh_destroy(str_set, string_set1);
+    kh_destroy(str_set, string_set2);
+    return sim;
+}

src/jaccard.h

@@ -7,5 +7,6 @@
 #include "collections.h"
 
 double jaccard_similarity(khash_t(str_set) *s1, khash_t(str_set) *s2);
+double jaccard_similarity_string_arrays(size_t num_strings1, char **strings1, size_t num_strings2, char **strings2);
 
 #endif