牛客-剑指0ffer-树的子结构

题目描述
输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）

/**
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) {
        boolean result = false;
        
        if (root1 != null && root2 != null){
            if (root1.val == root2.val){
                result = DoesTree1HasTree2(root1,root2);
            }
            if (!result){
                result = HasSubtree(root1.left,root2);
                
            }
            if (!result){
                result = HasSubtree(root1.right,root2);
            }
        }
        return result;
    }
    public boolean DoesTree1HasTree2(TreeNode root1,TreeNode root2){
        if (root1 == null && root2 != null){
            return false;
        }
        if (root2 == null){
            return true;
        }
        if (root1.val != root2.val){
            return false;
        }
        return DoesTree1HasTree2(root1.left,root2.left) && DoesTree1HasTree2(root1.right,root2.right);
    }
}