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CheckSubtree.java
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CheckSubtree.java
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package Leetcode;
import com.sun.source.tree.Tree;
/**
* @author kalpak
*
* Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s.
* A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.
*
* Example 1:
* Given tree s:
*
* 3
* / \
* 4 5
* / \
* 1 2
* Given tree t:
* 4
* / \
* 1 2
*
* Return true, because t has the same structure and node values with a subtree of s.
*
*
* Example 2:
* Given tree s:
*
* 3
* / \
* 4 5
* / \
* 1 2
* /
* 0
* Given tree t:
* 4
* / \
* 1 2
* Return false.
*
*/
public class CheckSubtree {
public static boolean isSubtree(TreeNode s, TreeNode t) {
if(s == null)
return false;
return isSameTree(s, t) || isSubtree(s.left, t) || isSubtree(s.right, t);
}
private static boolean isSameTree(TreeNode p, TreeNode q) {
if(p == null && q == null)
return true;
if(p == null || q == null)
return false;
if(p.val == q.val)
return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
else
return false;
}
public static void main(String[] args) {
TreeNode root1 = new TreeNode(3);
root1.left = new TreeNode(4);
root1.right = new TreeNode(5);
root1.left.left = new TreeNode(1);
root1.left.right = new TreeNode(2);
TreeNode root2 = new TreeNode(4);
root2.left = new TreeNode(1);
root2.right = new TreeNode(2);
System.out.println(isSubtree(root1, root2));
}
}