Make swapping letter cheaper.

server/src/suggest.ts

@@ -15,6 +15,8 @@ export interface Trie {
 }
 
 const baseCost = 100;
+const swapCost = 75;
+const postSwapCost = swapCost - baseCost;
 
 export interface SuggestionResult {
     word: string;
@@ -104,8 +106,10 @@ export function suggestA(
             let min = matrix[d][0];
             for (let i = 1; i <= mx; ++i) {
                 const curLetter = x[i];
-                const subCost = (w === curLetter || (curLetter === lastSugLetter && w === lastLetter))
-                    ? 0 : baseCost;
+                const subCost =
+                    (w === curLetter)
+                    ? 0 : ((curLetter === lastSugLetter && w === lastLetter)
+                    ? postSwapCost : baseCost);
                 matrix[d][i] = Math.min(
                     matrix[d - 1][i - 1] + subCost, // substitute
                     matrix[d - 1][i] + baseCost,    // insert

server/test/suggest_test.ts

@@ -71,6 +71,19 @@ describe('test suggestions', () => {
     });
 });
 
+describe('matching hte', () => {
+    const words = [
+        'ate', 'hoe', 'hot', 'the', 'how', 'toe'
+    ];
+
+    const trie = wordListToTrie(words);
+
+    it('checks best match', () => {
+        const results = suggest(trie, 'hte');
+        console.log(JSON.stringify(results, null, 4));
+    });
+});
+
 describe('test for duplicate suggestions', () => {
     const words = [
         'apple', 'ape', 'able', 'apples', 'banana', 'orange', 'pear', 'aim', 'approach', 'bear'
@@ -146,6 +159,13 @@ describe('test suggestions for large vocab', function() {
             console.log(suggestions);
         });
     });
+
+    it('checks best match for "hte"', () => {
+        return pTrie.then(trie => {
+            const results = suggest(trie, 'hte');
+            console.log(JSON.stringify(results, null, 4));
+        });
+    });
 });
 
 /*  */