原题链接: https://oj.leetcode.com/problems/same-tree/

public boolean isSameTree(TreeNode p, TreeNode q) {
    if (p == null && q == null || p == q) {
        return true;
    } else if (p == null || q == null) {
        return false;
    }

    if (!isSameTree(p.left, q.left)) return false;
    if (!isSameTree(p.right, q.right)) return false;
    if (p.val == q.val) return true;

    return false;
}