JZ17 tree substructure

Title description

Enter two binary trees A and B to determine whether B is a substructure of A. (Ps: We agree that the empty tree is not a substructure of any tree)

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    
    
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
    
    
        //判断特殊情况
        if(root1 ==null || root2 == null) return false;
        return isSubtree(root1,root2) || HasSubtree(root1.left,root2) || HasSubtree(root1.right,root2);
    }

    private boolean isSubtree(TreeNode root1,TreeNode root2) {
    
    
        if (root2 == null) return true;
        if (root1 == null) return false;

        if (root1.val == root2.val) {
    
    
            return isSubtree(root1.left,root2.left)  && isSubtree(root1.right,root2.right);
        }
        return false;
    }
}