Design Compressed String Iterator

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Problem

A compressed string is a sequence of letter-count pairs: each English letter is immediately followed by a positive decimal count of how many times it repeats. For example "a2B10" stands for two as followed by ten Bs. Counts can have several digits and can be very large. Implement StringIterator(compressedString): - next() returns the next character of the uncompressed string. If every character has already been returned, it returns a single space " ". - hasNext() returns true if at least one character has not been returned yet. Do not expand the string; counts may be as large as 10^9.

Examples

Input: ["StringIterator","next","next","hasNext","next","hasNext","next"] [["a2B1"],[],[],[],[],[],[]]
Output: [null,"a","a",true,"B",false," "]
The uncompressed string is "aaB". After returning all three characters, `hasNext` is false and `next` returns a space.
Input: ["StringIterator","next","next","hasNext"] [["k12m1"],[],[],[]]
Output: [null,"k","k",true]
The count 12 has two digits, so "k" repeats 12 times; plenty remain after two calls.

Constraints

  • 1 <= compressedString.length <= 1000
  • `compressedString` alternates an English letter and a count with 1 <= count <= 10^9
  • At most 100 calls to `next` and `hasNext`

What the interviewer grades

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