perf: better damerau levenshtein

.vscode/settings.json

@@ -5,6 +5,6 @@
   "editor.formatOnPaste": true,
   "editor.wordWrap": "on",
   "editor.codeActionsOnSave": {
-    "source.organizeImports": true
+    "source.organizeImports": "explicit"
   }
 }

src/dev/math/DamerauLevenshtein.ts

@@ -1,28 +1,25 @@
-export function damerauLevenshtein(s1: string, s2: string): number {
-  const s1len = s1.length;
-  const s2len = s2.length;
+function damerauLevenshtein(s1: string, s2: string): number {
+  if (s1 === s2) return 0;
+
+  const [s1len, s2len] = [s1.length, s2.length];
   const matrix: number[][] = Array.from({ length: s1len + 1 }, () => new Array(s2len + 1).fill(0));
 
-  for (let i: number = 1; i <= s1len; i++) {
-    matrix[i][0] = i;
-  }
+  for (let y = 1; y <= s1len; y++) matrix[y][0] = y;
+  for (let x = 1; x <= s2len; x++) matrix[0][x] = x;
 
-  for (let j: number = 1; j <= s2len; j++) {
-    matrix[0][j] = j;
-  }
-
-  for (let i: number = 1; i <= s1len; i++) {
-    for (let j: number = 1; j <= s2len; j++) {
-      if (s1[i - 1] === s2[j - 1]) {
-        matrix[i][j] = matrix[i - 1][j - 1];
+  for (let y = 1; y <= s1len; y++) {
+    for (let x = 1; x <= s2len; x++) {
+      if (s1[y - 1] === s2[x - 1]) {
+        matrix[y][x] = matrix[y - 1][x - 1];
       } else {
-        matrix[i][j] = 1 + Math.min(matrix[i - 1][j], matrix[i][j - 1], matrix[i - 1][j - 1]);
-        if (i > 1 && j > 1 && s1[i - 1] === s2[j - 2] && s1[i - 2] === s2[j - 1]) {
-          matrix[i][j] = Math.min(matrix[i][j], matrix[i - 2][j - 2] + 1);
+        matrix[y][x] = 1 + Math.min(matrix[y - 1][x], matrix[y][x - 1], matrix[y - 1][x - 1]);
+        if (y > 1 && x > 1 && s1[y - 1] === s2[x - 2] && s1[y - 2] === s2[x - 1]) {
+          matrix[y][x] = Math.min(matrix[y][x], matrix[y - 2][x - 2] + 1);
         }
       }
     }
   }
+
   return matrix[s1len][s2len];
 }