Mini Parser
Given a string representing a nested integer list (e.g., [123,[456,[789]]]), parse it and return the flattened integers.
Output space-separated integers in order.
Example:
[123,[456,[789]]]
123 456 789
- The input string
[123,[456,[789]]]is parsed as a nested list of integers. - The outermost list is processed first, yielding the integer
123. - The inner list
[456,[789]]is then processed, yielding the integer456and another inner list[789]. - The innermost list
[789]is processed last, yielding the integer789, resulting in the final output:123 456 789.
Constraints:
- String is well-formed
- Integers may be negative
- Nesting depth <= 50
Background Knowledge
The "Mini Parser" problem involves parsing a string that represents a nested integer list. To tackle this problem, it's essential to understand the concept of nested structures, which are data structures that contain other instances of the same data structure. In this case, we're dealing with a nested list of integers, where each element can be either an integer or another list. This type of structure is commonly represented using recursion, where a function calls itself to process each nested element.
To parse the input string, we need to understand the basics of parsing, which is the process of analyzing a string of symbols to determine its structure and meaning. In this case, we'll use a simple parsing approach to extract the integers from the input string. We'll also need to use iterators to traverse the nested list and extract the integers in the correct order. Iterators are objects that allow us to iterate over a sequence of elements, such as a list or a string, without having to know the underlying implementation details.
The problem also requires us to output the flattened integers in order, which means we need to understand the concept of traversal, where we visit each element in the nested list in a specific order. In this case, we'll use a depth-first traversal approach, where we visit each element in the nested list recursively, from left to right. This approach will allow us to extract the integers in the correct order and output them as a space-separated string.
Algorithm/Approach
The general approach to solving this type of problem involves using a recursive descent parser, which is a top-down parsing technique that uses recursive functions to parse the input string. We'll use a recursive function to parse each nested list and extract the integers, and then use an iterator to traverse the parsed list and output the integers in the correct order. The algorithm will involve the following steps:
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