dfs = (p, q) => {
    const left = isSameTree(p.left, q.left);
    const right = isSameTree(p.right, q.right);

    return left && right;
}
* https://leetcode.com/problems/same-tree/
* Time complexity is O(N), where N is the total number of nodes in the tree.
This is because in the worst-case scenario, we need to visit every node once.
* Space complexity is O(H), where H is the height of the tree.
This is because in the worst-case scenario (a skewed tree), the maximum
amount of space is consumed by the recursive stack. 
@param {*} p 
@param {*} q 
@returns