(主函数递归寻找匹配的首节点，dfs函数递归进行递归匹配) 树的子结构 Leetcode 48

class Solution {
    public boolean isSubStructure(TreeNode A, TreeNode B) {

        if(A == null || B ==null){
            return false;
        }

        return dfs(A,B) || dfs(A,B) || isSubStructure(A.left,B) || isSubStructure(A.right, B);


    }

    public boolean dfs(TreeNode A , TreeNode B){

        if(B == null){
            return true;
        }
        if(A == null && B != null){
            return false;
        }
        if(A.val == B.val){
            return dfs(A.left,B.left) && dfs(A.right,B.right);
        }
        return false;

    }

}