Java
/*
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 Subtree_of_Another_Tree {
public static void main(String[] args) {
Subtree_of_Another_Tree out = new Subtree_of_Another_Tree();
Solution s = out.new Solution();
TreeNode root = new TreeNode(3);
root.left = new TreeNode(4);
root.right = new TreeNode(5);
root.left.left = new TreeNode(1);
root.left.right = new TreeNode(2);
TreeNode t = new TreeNode(4);
t.left = new TreeNode(1);
t.right = new TreeNode(2);
System.out.println(s.isSubtree(root, t));
}
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSubtree(TreeNode s, TreeNode t) {
if(s == null && t == null) {
return true;
}
if((s == null && t != null) || (s != null && t == null)) {
return false;
}
// key is to have a same tree check, or else will be skip level same
return isSameTree(s, t) || isSubtree(s.left, t) || (isSubtree(s.right, t));
}
public boolean isSameTree(TreeNode s, TreeNode t) {
if(s == null && t == null) {
return true;
}
if((s == null && t != null) || (s != null && t == null)) {
return false;
}
return s.val == t.val && isSameTree(s.left, t.left) && isSameTree(s.right, t.right);
}
}
}Java
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isSubtree(TreeNode s, TreeNode t) {
if (s == null)
return t == null;
if (t == null || same(s, t))
return true;
return isSubtree(s.left, t) || isSubtree(s.right, t);
}
public boolean same(TreeNode s, TreeNode t) {
if (s == null && t == null)
return true;
if (s == null || t == null)
return false;
return s.val == t.val && same(s.left, t.left) && same(s.right, t.right);
}
}