Function hashify

javascript/0572-subtree-of-another-tree.js:68–82

(root, hash, postOrderKey)

};

const hashify = (root, hash, postOrderKey) => {
    if (!root) return '#';

    const left = hashify(root.left, hash, postOrderKey);
    const right = hashify(root.right, hash, postOrderKey);

    const key = [left, root.val, right].join('');

    if (!hash.has(key)) {
        hash.set(key, postOrderKey[0]);
        postOrderKey[0]++;
    }

    return hash.get(key);
};

var isSubtree = function (root, subRoot, hash = new Map(), postOrderKey = [0]) {
    hashify(root, hash, postOrderKey);