Data commit

Task/Levenshtein-distance/Objective-C/levenshtein-distance.m

@@ -0,0 +1,35 @@
+@interface NSString (levenshteinDistance)
+- (NSUInteger)levenshteinDistanceToString:(NSString *)string;
+@end
+
+@implementation NSString (levenshteinDistance)
+- (NSUInteger)levenshteinDistanceToString:(NSString *)string {
+    NSUInteger sl = [self length];
+    NSUInteger tl = [string length];
+    NSUInteger *d = calloc(sizeof(*d), (sl+1) * (tl+1));
+
+#define d(i, j) d[((j) * sl) + (i)]
+    for (NSUInteger i = 0; i <= sl; i++) {
+        d(i, 0) = i;
+    }
+    for (NSUInteger j = 0; j <= tl; j++) {
+        d(0, j) = j;
+    }
+    for (NSUInteger j = 1; j <= tl; j++) {
+        for (NSUInteger i = 1; i <= sl; i++) {
+            if ([self characterAtIndex:i-1] == [string characterAtIndex:j-1]) {
+                d(i, j) = d(i-1, j-1);
+            } else {
+                d(i, j) = MIN(d(i-1, j), MIN(d(i, j-1), d(i-1, j-1))) + 1;
+            }
+        }
+    }
+
+    NSUInteger r = d(sl, tl);
+#undef d
+
+    free(d);
+
+    return r;
+}
+@end