Subtree of Another Tree

This question is similar to check if two trees are symmetric or not.

https://leetcode.com/problems/subtree-of-another-tree/

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 that 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.

Here is the Solution:

/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
String s1= "";
public boolean isSubtree(TreeNode s, TreeNode t) {
if(t==null)
return true;
if(s == null)
return false;
if(isSymmetric(s,t))
return true;
return isSubtree(s.left,t) || isSubtree(s.right,t);
}

public static boolean isSymmetric(TreeNode left,TreeNode right){
if(left == null || right == null)
return left == right;
if(left.val!=right.val)
return false;
return isSymmetric(left.left,right.left) && isSymmetric(left.right,right.right);
}
}

Thank you for Reading!

Happy Coding!

Software Developer

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