MathOpt - Sudoku Generator

import { initMathOpt, MathOpt } from 'or-tools-wasm/mathopt';

await initMathOpt();

function varIndex(row: number, col: number, digit: number) {
  return (row * 9 + col) * 9 + (digit - 1);
}

const model = MathOpt.Model('sudoku');
const x = Array.from({ length: 9 * 9 * 9 }, (_, index) =>
  model.addBinaryVariable({ name: `x_${index}` }),
);
const exactlyOne = (vars: typeof x) =>
  model.addLinearConstraint({
    lowerBound: 1,
    upperBound: 1,
    terms: vars.map((variable) => ({ variable, coefficient: 1 })),
  });

for (let row = 0; row < 9; row++) {
  for (let col = 0; col < 9; col++) {
    exactlyOne(Array.from({ length: 9 }, (_, digit) => x[varIndex(row, col, digit + 1)]));
  }
}
for (let row = 0; row < 9; row++) {
  for (let digit = 1; digit <= 9; digit++) {
    exactlyOne(Array.from({ length: 9 }, (_, col) => x[varIndex(row, col, digit)]));
  }
}
for (let col = 0; col < 9; col++) {
  for (let digit = 1; digit <= 9; digit++) {
    exactlyOne(Array.from({ length: 9 }, (_, row) => x[varIndex(row, col, digit)]));
  }
}
for (let boxRow = 0; boxRow < 3; boxRow++) {
  for (let boxCol = 0; boxCol < 3; boxCol++) {
    for (let digit = 1; digit <= 9; digit++) {
      exactlyOne([0, 1, 2].flatMap((rowOffset) =>
        [0, 1, 2].map((colOffset) =>
          x[varIndex(boxRow * 3 + rowOffset, boxCol * 3 + colOffset, digit)]),
      ));
    }
  }
}

model.minimize([]);
const solverType = MathOpt.SolverType.CP_SAT;
const result = await MathOpt.solve(model, {
  solverType,
  threads: 4,
  solutionLimit: 1,
  cpSat: { numWorkers: 4, stopAfterFirstSolution: true },
});
console.log(result.terminationReason, result.variableValues);