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,[789]]]",

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.

Solution

# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    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]
#        """

from collections import deque

class Solution(object):
    def deserialize(self, s):
        """
        :type s: str
        :rtype: NestedInteger
        """
        initial = NestedInteger()
        i = 0
        q = deque()
        q.append(initial)

        while i < len(s):
            if s[i] == "[":
                n = NestedInteger()
                q[-1].add(n)
                q.append(n)
                i += 1
            elif s[i] == "]":
                q.pop()
                i += 1
            elif s[i] == ",":
                i+=1
            else:
                j = i
                while j < len(s) and ('0' <= s[j] <= '9' or s[j] == '-'):
                    j+=1
                q[-1].add(int(s[i:j]))
                i = j
        return q[0].getList()[0]