[LintCode] 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.

Solution

public class solution {
    public boolean isIdentical(TreeNode a, TreeNode b) {
        if (a == null && b == null) return true;
        if (a == null || b == null) return false;
        return a.val == b.val && isIdentical(a.left, b.left) && isIdentical(a.right, b.right);
    }
}