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);
        }
    }
}