Sword refers to the substructure of the Offer-24 tree

/**
 * Do not move A to traverse B first
 * @author Lucas
 * @date 2021/02/08 23:31
 * @param A given tree
 * @param B substructure
 * @return boolean
 */
public static boolean isSubStructure(TreeNode A, TreeNode B) {
    // Recursive exit
    if (A == null || B == null) {
        return false;
    }
    // Recursively find the subtree rooted in A with the root node of B as the root
    return compare(A, B) || isSubStructure(A.left, B) || isSubStructure(A.right, B);
}

/**
 * A, B compare to determine whether B is a substructure of A
 * @author Lucas
 * @date 2021/02/08 23:32
 * @param A given tree
 * @param B substructure
 * @return boolean
 */
public static boolean compare(TreeNode A, TreeNode B){
    // When B is empty, it proves that the matching has been completed
    if (B == null){
        return true;
    }
    if (A == null || A.val != B.val){
        return false;
    }
    // Recursive AB to the left or right at the same time
    return compare(A.left, B.left) && compare(A.right, B.right);
}