0572-subtree-of-another-tree.java

// Solution: Recursive Approach

// Time Complexity: O(n)
// Extra Space Complexity: O(n)
class Solution {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if (subRoot == null || isSameTree(root, subRoot)) return true;
        if (root == null) return false;

        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
    }

    private boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null && q == null) {
            return true;
        }
    
        if (p == null || q == null || p.val != q.val) {
            return false;
        }

        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}