# Question

Formatted question description: https://leetcode.ca/all/385.html

 385	Mini Parser

Given a nested list of integers represented as a string, implement a parser to deserialize it.

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

Note: You may assume that the string is well-formed:
String is non-empty.
String does not contain white spaces.
String contains only digits 0-9, [, - ,, ].

Example 1:

Given s = "324",

You should return a NestedInteger object which contains a single integer 324.

Example 2:

Given s = "[123,[456,]]",

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.

@tag-stack


# Algorithm

First judge whether s is empty, and return directly if it is empty.

If it is not empty, see if the first character is [,

• If it is not, s is an integer, and we return the result directly.
• If the first character is [,
• And the length of s is less than or equal to 2, indicating that there is no content, and the result is returned directly.
• On the other hand, if the length of s is greater than 2, we start traversing from i=1, we need a variable start to record the start position of a certain layer, and use cnt to record whether the actual position is the same depth, cnt=0 means Same depth.

Since each paragraph in the middle is separated by a comma, when we judge that cnt is 0, and the current character is a comma or has reached the end of the string, we take out the string between start and the current position to call the function recursively, Add the returned result to res, and then update start to i+1.

• If you encounter [, the counter cnt increments by 1,
• If encountering ], the counter cnt will decrement by 1

Java