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)
思路:利用递归判断结点本身以及左右孩子
ac代码:
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 import java.util.ArrayList; 15 public class Solution { 16 public boolean HasSubtree(TreeNode root1,TreeNode root2) { 17 if(root1 == null&&root2 != null)return false; 18 if(root2 == null)return false; 19 boolean flag = false; 20 if(root1 != null&&root2 != null){ 21 if(root1.val == root2.val){ 22 flag = isSame(root1,root2); 23 } 24 if(!flag){ 25 flag = HasSubtree(root1.left,root2); 26 } 27 if(!flag){ 28 flag = HasSubtree(root1.right,root2); 29 } 30 } 31 return flag; 32 } 33 static boolean isSame(TreeNode t1,TreeNode t2){ 34 if(t1==null&&t2!=null) 35 return false; 36 if(t2==null) 37 return true; 38 if(t1.val==t2.val){ 39 40 return isSame(t1.left,t2.left)&&isSame(t1.right,t2.right); 41 }else 42 return false; 43 44 } 45 }