https://sisisinout.glitch.me/?size=15x15

sisisinoutSolverKai.js

function solve() {

    // a / b
    function modDiv(a, b, p) {
        function repeatSquares(x, n) {
            if (n === 0)
                return 1
            else if (n % 2 === 0)
                return repeatSquares(x*x % p, n/2)
            else
                return (x * repeatSquares(x*x % p, n/2)) % p
        }

        const numer = a % p
        const denom = repeatSquares(b, p-2)

        return (numer * denom) % p
    }


    function rowReduction(mat, dim) {
        const mod = 2
        
        // 行の0化
        for (let y=0; y < dim; y++) {
            // swapフェーズ
            if (mat[y][y] === 0) {
                for (let k=y+1; k < dim; k++) {
                    if (mat[k][y] !== 0) {
                        tmp = mat[y].slice()
                        mat[y] = mat[k].slice()
                        mat[k] = tmp
                        break
                    }
                }
            }
            
            const divisor = mat[y][y]
            for (let x=0; x <= dim; x++)
                mat[y][x] = modDiv(mat[y][x], divisor, mod)

            for (let k=0; k < dim; k++) {
                const coeff = mat[k][y]
                if (k != y) {
                    for (let x=0; x <= dim; x++) {
                        mat[k][x] -= mat[y][x] * coeff
                        mat[k][x] %= mod
                    }
                }
            }
        }

        let res = []
        for (let i=0; i < dim; i++) {
            res.push(Math.round(mat[i][dim]))
        }
        
        return res;
    }

    function nyanToClockwise(nyan) {
        return (Number(nyan.getAttribute("data-deg")) / (-90) + 4) % 4
    }


    const board = document.getElementsByClassName('nyan')
    const nyans = Array.from(board).map(nyan => nyanToClockwise(nyan))

    const elemNum = nyans.length
    const side = Math.round(Math.sqrt(elemNum))

    function inField(x, y) {
        return 0 <= x && x < side && 0 <= y && y < side
    }

    function mk4Dir(x, y) {
        return [[x-1, y], [x+1, y], [x, y-1], [x, y+1]];
    }


    // phase1
    let equations1 = new Array(elemNum);
    for (let i=0; i < elemNum; i++)
        equations1[i] = new Array(elemNum+1).fill(0);


    // write Equation
    for (let i=0; i < elemNum; i++) {
        equations1[i][i] += 1
        for (const p of mk4Dir(i%side, Math.floor(i/side))) {
            const [x, y] = p
            if (inField(x, y))
                equations1[i][y*side + x] -= 1
        }
        equations1[i][elemNum] = Math.abs(nyans[i] % 2)
    }

    let equations2 = JSON.parse(JSON.stringify(equations1))
    
    const ans1 = rowReduction(equations1, elemNum).map(x => Math.abs(x))

    
    // phase2
    for (let i=0; i < elemNum; i++) {
        if (ans1[i]) {
            nyans[i] -= 1
            for (const p of mk4Dir(i%side, Math.floor(i/side))) {
                const [x, y] = p
                if (inField(x, y))
                    nyans[y*side + x] += 1
            }
        }
    }
    nyans.forEach(nyan => ((nyan % 4) + 4) % 4)

    console.log(nyans)
    
    // write Equation
    for (let i=0; i < elemNum; i++) {
        equations2[i][elemNum] = nyans[i] / 2
    }

    const ans2 = rowReduction(equations2, elemNum).map(x => Math.abs(x))
    const ans = []

    for (let i=0; i < elemNum; i++)
        for (let k=0; k < ans1[i] + ans2[i] * 2; k++)
            ans.push(i)
    
    for(var i = ans.length - 1; i > 0; i--){
        var r = Math.floor(Math.random() * (i + 1));
        var tmp = ans[i];
        ans[i] = ans[r];
        ans[r] = tmp;
    }

    for (let i = 0; i < ans.length; i++) {
        setTimeout(() => board[ans[i]].click(), 10*i)
    }
}

solve()