0385. Mini Parser

https://leetcode.com/problems/mini-parser

Description

Given a string s represents the serialization of a nested list, implement a parser to deserialize it and return the deserialized NestedInteger.

Each element is either an integer or a list whose elements may also be integers or other lists.

Example 1:

**Input:** s = "324"
**Output:** 324
**Explanation:** You should return a NestedInteger object which contains a single integer 324.

Example 2:

**Input:** s = "[123,[456,[789]]]"
**Output:** [123,[456,[789]]]
**Explanation:** Return a NestedInteger object containing a nested list with 2 elements:
1. An integer containing value 123.
2. A nested list containing two elements:
    i.  An integer containing value 456.
    ii. A nested list with one element:
         a. An integer containing value 789

Constraints:

• 1 <= s.length <= 5 * 104

• s consists of digits, square brackets "[]", negative sign '-', and commas ','.

• s is the serialization of valid NestedInteger.

• All the values in the input are in the range [-106, 106].

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