Log the number of dancing link updates

src/sudoku/math.ts

@@ -166,6 +166,7 @@ export class SudokuMath {
     const [header, dlxRows] = this.getDLXHeader(); // complete header - no candidates removed
 
     let solutions = 0;
+    let updates = 0;
     const dlx = new DLX(header, () => ++solutions >= 2);
 
     const candidates: DNode[][] = Array.from(Array(this.values2), () =>
@@ -183,6 +184,7 @@ export class SudokuMath {
     const hasOneSolution = () => {
       solutions = 0;
       dlx.search();
+      updates += dlx.updates;
       return solutions === 1;
     };
 
@@ -248,6 +250,7 @@ export class SudokuMath {
     removed.forEach((index) => {
       completed[index] = 0;
     });
+    console.log("DLX updates:", updates);
     return completed;
   }