Topic
- Tree
Description
https://leetcode.com/problems/subtree-of-another-tree/
Given the roots of two binary trees root
and subRoot
, return true
if there is a subtree of root with the same structure and node values of subRoot
and false
otherwise.
A subtree of a binary tree tree
is a tree that consists of a node in tree
and all of this node's descendants. The tree tree
could also be considered as a subtree of itself.
Example 1:
Input: root = [3,4,5,1,2], subRoot = [4,1,2]
Output: true
Example 2:
Input: root = [3,4,5,1,2,null,null,null,null,0], subRoot = [4,1,2]
Output: false
Constraints:
- The number of nodes in the
root
tree is in the range [1, 2000]. - The number of nodes in the
subRoot
tree is in the range [1, 1000]. - $-10^4 <= root.val <= 10^4$
- $-10^4 <= subRoot.val <= 10^4$
Analysis
考查前序遍歷。
Submission
import com.lun.util.BinaryTree.TreeNode;
public class SubtreeOfAnotherTree {
public boolean isSubtree(TreeNode root, TreeNode subRoot) {
if(root == null ^ subRoot == null)
return false;
if(equals(root, subRoot))
return true;
return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
}
public boolean equals(TreeNode node1, TreeNode node2) {
if(node1 == null ^ node2 == null)
return false;
if(node1 != null && node2 != null) {
if(node1.val != node2.val)
return false;
return equals(node1.left, node2.left) && //
equals(node1.right, node2.right);
}
return true;
}
}
Test
import static org.junit.Assert.*;
import static com.lun.util.BinaryTree.*;
import org.junit.Test;
public class SubtreeOfAnotherTreeTest {
@Test
public void test() {
SubtreeOfAnotherTree obj = new SubtreeOfAnotherTree();
assertTrue(obj.isSubtree(integers2BinaryTree(3, 4, 5, 1, 2), //
integers2BinaryTree(4, 1, 2)));
assertFalse(obj.isSubtree(integers2BinaryTree(3, 4, 5, 1, 2, null, null, null, null, 0),//
integers2BinaryTree(4, 1, 2)));
}
}