Add back short-circuit optimizations to avoid array allocations on empty strings for OSA, Lev, and Weighted Lev

Author: paulirwin

src/main/java/info/debatty/java/stringsimilarity/Levenshtein.java

@@ -50,6 +50,14 @@ public final double distance(final String s1, final String s2) {
             return 0;
         }
 
+        if (s1.length() == 0) {
+            return s2.length();
+        }
+
+        if (s2.length() == 0) {
+            return s1.length();
+        }
+
         // create two work vectors of integer distances
         int[] v0 = new int[s2.length() + 1];
         int[] v1 = new int[s2.length() + 1];

src/main/java/info/debatty/java/stringsimilarity/OptimalStringAlignment.java

@@ -65,6 +65,14 @@ public final double distance(final String s1, final String s2) {
 
         int n = s1.length(), m = s2.length();
 
+        if (n == 0) {
+            return m;
+        }
+
+        if (m == 0) {
+            return n;
+        }
+
         // Create the distance matrix H[0 .. s1.length+1][0 .. s2.length+1]
         int[][] d = new int[n + 2][m + 2];
 

src/main/java/info/debatty/java/stringsimilarity/WeightedLevenshtein.java

@@ -64,6 +64,14 @@ public final double distance(final String s1, final String s2) {
             return 0;
         }
 
+        if (s1.length() == 0) {
+            return s2.length();
+        }
+
+        if (s2.length() == 0) {
+            return s1.length();
+        }
+
         // create two work vectors of integer distances
         double[] v0 = new double[s2.length() + 1];
         double[] v1 = new double[s2.length() + 1];