Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

• Time complexity : O(2n) = O(n). where n is a number of nodes in a tree. We visit each node in both trees exactly once.

• Space complexity : O(log(n)) - best, o(n) worst. The best case is two completely balanced trees. The worst case is two completely unbalanced trees, to keep a recursion stack.