Identical Binary Tree

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.

are not identical.

Solution 1: DFS

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