Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

public class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null && q == null) return true;
        if (p == null || q == null) return false;
        return p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}

class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """

        if not p and not q:
            return True
        if not p or not q:
            return False

        if p.val == q.val
            return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right):
        return False