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TypeScript

import fc from "fast-check";
import { describe, expect, it } from "vitest";
import {
classicRegions,
isSolved,
type PuzzleDefinition,
} from "../../src/domain";
import {
countSolutions,
generateClassic,
minimizePuzzle,
solveExact,
} from "../../src/solver";
const solution4 = [1, 2, 3, 4, 3, 4, 1, 2, 4, 3, 2, 1, 2, 1, 4, 3] as const;
const puzzle4: PuzzleDefinition = {
version: 1,
size: 4,
givens: [1, 0, 0, 4, 0, 4, 1, 0, 4, 0, 2, 0, 0, 1, 0, 3],
regions: classicRegions(4),
constraints: [],
};
describe("exact solver", () => {
it("solves a classic puzzle with MRV without mutating its input", () => {
const original = [...puzzle4.givens];
const result = solveExact(puzzle4);
expect(result.count).toBe(1);
expect(result.solutions[0]).toEqual(solution4);
expect(result.truncated).toBe(false);
expect(puzzle4.givens).toEqual(original);
expect(isSolved(puzzle4, result.solutions[0] ?? [])).toBe(true);
});
it("caps solution counting and reports that unexplored work remains", () => {
const empty: PuzzleDefinition = {
...puzzle4,
givens: new Array<number>(16).fill(0),
};
const result = solveExact(empty, { maxSolutions: 2 });
expect(result.count).toBe(2);
expect(result.truncated).toBe(true);
expect(result.limitReason).toBe("solution-cap");
expect(countSolutions(empty)).toBe(2);
});
it("solves a puzzle combining supported local constraints", () => {
const variant: PuzzleDefinition = {
...puzzle4,
givens: solution4.map((value, cell) => (cell % 3 === 0 ? 0 : value)),
constraints: [
{ type: "diagonal", direction: "main" },
{ type: "diagonal", direction: "anti" },
{ type: "killer-cage", cells: [0, 1], sum: 3 },
{ type: "thermo", cells: [0, 1, 2, 3] },
{ type: "arrow", bulb: [3], line: [0, 2] },
{ type: "kropki", a: 0, b: 1, kind: "black" },
{ type: "xv", a: 0, b: 3, total: 5 },
{ type: "inequality", lesser: 0, greater: 1 },
{ type: "renban", cells: [0, 1, 2, 3] },
{ type: "palindrome", cells: [0, 6] },
],
};
expect(solveExact(variant).solutions[0]).toEqual(solution4);
});
it("generates deterministic, unique 4x4 puzzles for arbitrary seeds", () => {
fc.assert(
fc.property(fc.integer(), (seed) => {
const generated = generateClassic({
size: 4,
seed,
targetClues: 8,
symmetry: "rotational",
});
const again = generateClassic({
size: 4,
seed,
targetClues: 8,
symmetry: "rotational",
});
expect(generated.givens).toEqual(again.givens);
const checked = solveExact(generated, { maxSolutions: 2 });
expect(checked.count).toBe(1);
expect(checked.truncated).toBe(false);
expect(checked.solutions[0]).toEqual(generated.solution);
}),
{ numRuns: 12 },
);
});
it("minimizes only when uniqueness is retained", () => {
const full: PuzzleDefinition = {
version: 1,
size: 4,
givens: solution4,
solution: solution4,
regions: classicRegions(4),
constraints: [],
};
const minimized = minimizePuzzle(full, {
seed: "minimal",
targetClues: 6,
symmetry: "none",
});
expect(minimized.givens.filter(Boolean).length).toBeLessThan(16);
expect(solveExact(minimized).count).toBe(1);
});
it("generates a practical uniquely solvable 9x9 puzzle", () => {
const generated = generateClassic({
size: 9,
seed: "nine-by-nine",
targetClues: 35,
symmetry: "rotational",
maxChecks: 60,
solveTimeoutMs: 2_000,
});
expect(generated.givens.filter(Boolean).length).toBeGreaterThanOrEqual(35);
const result = solveExact(generated, { timeoutMs: 5_000 });
expect(result.count).toBe(1);
expect(result.truncated).toBe(false);
expect(result.solutions[0]).toEqual(generated.solution);
});
});