【剑指OFFER】树的子结构

 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 }