Mini Parser — LeetCode 385 Python Solution

# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
# class NestedInteger:
#    def __init__(self, value=None):
#        """
#        If value is not specified, initializes an empty list.
#        Otherwise initializes a single integer equal to value.
#        """
#
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def add(self, elem):
#        """
#        Set this NestedInteger to hold a nested list and adds a nested integer elem to it.
#        :rtype void
#        """
#
#    def setInteger(self, value):
#        """
#        Set this NestedInteger to hold a single integer equal to value.
#        :rtype void
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """
class Solution:
    def deserialize(self, s: str) -> NestedInteger:
        if not s or s == '[]':
            return NestedInteger()
        if s[0] != '[':
            return NestedInteger(int(s))
        ans = NestedInteger()
        depth, j = 0, 1
        for i in range(1, len(s)):
            if depth == 0 and (s[i] == ',' or i == len(s) - 1):
                ans.add(self.deserialize(s[j:i]))
                j = i + 1
            elif s[i] == '[':
                depth += 1
            elif s[i] == ']':
                depth -= 1
        return ans