Spiral traversal

spiral_walk.js

const arr_odd = [
    [1,   2,  3,  4, 5],
    [16, 17, 18, 19, 6],
    [15, 24, 25, 20, 7],
    [14, 23, 22, 21, 8],
    [13, 12, 11, 10, 9]
];

const arr_even = [
    [1,   2,  3,  4,  5,  6],
    [20, 21, 22, 23, 24,  7],
    [19, 32, 33, 34, 25,  8],
    [18, 31, 36, 35, 26,  9],
    [17, 30, 29, 28, 27, 10],
    [16, 15, 14, 13, 12, 11]
];

// U -> R
// R -> D
// D -> L
// L -> U
function walk(arr) {
    const result = [];
    const size = arr[0].length;
    function up(row, col, limit) {
        if (!limit) return;
        let t = limit;
        while (t--) result.push(arr[row--][col]);
        right(row + 1, col + 1, limit);
    }
    function right(row, col, limit) {
        if (!limit) return;
        let t = limit;
        while (t--) result.push(arr[row][col++]);
        down(row + 1, col - 1, limit - 1);
    }
    function down(row, col, limit) {
        if (!limit) return;
        let t = limit;
        while (t--) result.push(arr[row++][col]);
        left(row - 1, col - 1, limit);
    }
    function left(row, col, limit) {
        if (!limit) return;
        let t = limit;
        while (t--) result.push(arr[row][col--]);
        up(row - 1, col + 1, limit - 1);
    }

    right(0, 0, size)

    return result;
}

function check(result, size) {
    const correct = [];
    let t = size * size
    while (t--) correct.unshift(t + 1);
    while (size--) 
        if (result[size-1] !== correct[size-1]) 
            throw new Error("wrong answer")
    return "correct answer"
}

console.log(check(walk(arr_odd), arr_odd.length));
console.log(check(walk(arr_even), arr_even.length));