You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way.
The null
node needs to be represented by empty parenthesis pair "()"
. And you need to omit all the empty parenthesis pairs that don't affect the one-to-one mapping relationship between the string and the original binary tree.
Example 1:
Input: Binary tree: [1,2,3,4] 1 / 2 3 / 4 Output: "1(2(4))(3)" Explanation: Originallay it needs to be "1(2(4)())(3()())", but you need to omit all the unnecessary empty parenthesis pairs. And it will be "1(2(4))(3)".
Example 2:
Input: Binary tree: [1,2,3,null,4] 1 / 2 3 4 Output: "1(2()(4))(3)" Explanation: Almost the same as the first example, except we can't omit the first parenthesis pair to break the one-to-one mapping relationship between the input and the output.
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