Given 2 [binary expression trees](https://en.wikipedia.org/wiki/Binary_expression_tree) `tree1` and `tree2`. The leaves of a binary expression tree are variable names and the other nodes contain operators. Find out if the expressions represented by these trees are equal or not.\nThere are only plus signs `+` and letters in the tree. Input is guaranteed to be valid.\n\n**Example 1:**\n```\nInput:\n\t tree1\n\t   +\n\t /   \\\n\ta     b\n\n\t tree2\n\t   +\n\t /   \\\n\tb     a\nOutput: true\nExplanation: a + b = b + a\n```\n\n**Example 2:**\n```\nInput:\n\t tree1\n\t\t+\n\t  /   \\\n\t a     +\n\t\t  / \\\n\t\t c   de\n\n\t tree2\n\t\t+\n\t  /   \\\n\t +     de\n\t/ \\\n   a   c\n\nOutput: true\nExplanation: a + (c + de) == (a + c) + de\n```\n\n**Example 3:**\n```\nInput:\n\t tree1\n\t   +\n\t /   \\\n\ta     b\n\n\t tree2\n\t   +\n\t /   \\\n\tc     d\nOutput: false\nExplanation: a + b != c + d\n```\n\n**Follow-up:**\nMinus `-` sign is allowed. For example\n```\n    +\n  /   \\\n a     -\n      / \\\n     c   d\n\na + (c - d)\n```

Given 2 binary expression trees tree1 and tree2. The leaves of a binary expression tree are variable names and the other nodes contain operators. Find out if th