# Identical Binary Tree

## Problem

Check if two binary trees are identical. Identical means the two binary trees have the same structure and every identical position has the same value.

## Example

        1             1
/ \           / \
2   2   and   2   2
/             /
4             4

are identical.

        1             1
/ \           / \
2   3   and   2   3
/               \
4                 4

are not identical.

## Code - Java

/**
* Definition of TreeNode:
* public class TreeNode {
*   public int val;
*   public TreeNode left, right;
*   public TreeNode(int val) {
*     this.val = val;
*     this.left = this.right = null;
*   }
* }
*/
public class Solution {
/**
* @param a, b, the root of binary trees.
* @return true if they are identical, or false.
*/
public boolean isIdentical(TreeNode a, TreeNode b) {
if (a == null && b == null) {
return true;
} else if (a == null || b == null) {
return false;
} else {
return a.val == b.val && isIdentical(a.left, b.left) && isIdentical(a.right, b.right);
}
}
}