【剑指OFFER】树的子结构

【问题描述】

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）

【AC 代码】

Reference: https://blog.nowcoder.net/n/78f8183e6b8b40208483978b80cd8f74?f=comment

 1 /**
 2 public class TreeNode {
 3     int val = 0;
 4     TreeNode left = null;
 5     TreeNode right = null;
 6
 7     public TreeNode(int val) {
 8         this.val = val;
 9
10     }
11
12 }
13 */
14 public class Solution {
15     public boolean HasSubtree(TreeNode root1,TreeNode root2) {
16         if (root1 == null || root2 == null) return false;
17         return DoesTree1HasTree2(root1, root2) || HasSubtree(root1.left, root2) || HasSubtree(root1.right, root2);
18     }
19     private boolean DoesTree1HasTree2(TreeNode tree1, TreeNode tree2) {
20         if (tree2 == null) return true;
21         if (tree1 == null) return false;
22         if (tree1.val != tree2.val) return false;
23         return DoesTree1HasTree2(tree1.left, tree2.left) && DoesTree1HasTree2(tree1.right, tree2.right);
24     }
25 }

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