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Goal Parser Interpretation

You own a Goal Parser that can interpret a string command. The command consists of an alphabet of "G", "()" and/or "(al)" in some order. The Goal Parser will interpret "G" as the string "G", "()" as the string "o", and "(al)" as the string "al". The interpreted strings are then concatenated in the original order.

Given the string command, return the Goal Parser's interpretation of command.

 

Example 1:

Input: command = "G()(al)"
Output: "Goal"
Explanation: The Goal Parser interprets the command as follows:
G -> G
() -> o
(al) -> al
The final concatenated result is "Goal".

Example 2:

Input: command = "G()()()()(al)"
Output: "Gooooal"

Example 3:

Input: command = "(al)G(al)()()G"
Output: "alGalooG"

 

Constraints:

  • 1 <= command.length <= 100
  • command consists of "G", "()", and/or "(al)" in some order.

Solution Explanation for Goal Parser Interpretation

The problem asks to interpret a string representing commands for a Goal Parser. The parser interprets 'G' as 'G', '()' as 'o', and '(al)' as 'al'. The goal is to produce the interpreted string.

Approach 1: String Replacement (More Efficient)

This approach leverages the built-in string replacement functions in various programming languages. It directly replaces all occurrences of "()" with "o" and "(al)" with "al". This is generally the most efficient method because these functions are highly optimized.

Time Complexity: O(n), where n is the length of the input string. String replacement operations, while seemingly simple, are often optimized in modern languages to have a linear time complexity in most cases. However, in some less-optimized implementations, it could be O(n^2) in the worst case.

Space Complexity: O(n) in the worst case, to store the resultant string. However, in some languages, the replacement functions might perform in-place operations, reducing this to O(1) extra space.

Code Examples: (See the previous response for code examples in various languages using this method)

Approach 2: String Iteration (Less Efficient but More Explicit)

This method iterates through the input string character by character. It handles each case explicitly:

  • If the character is 'G', add 'G' to the result.
  • If the character is '(', check the next character:
    • If it's ')', add 'o' to the result.
    • If it's 'a', add "al" to the result.

Time Complexity: O(n), as we iterate through the string once.

Space Complexity: O(n) in the worst case, to store the resultant string. This is unavoidable since we need to construct the interpreted string.

Code Examples: (See the previous response for code examples in various languages using this method)

Comparison of Approaches

The string replacement approach (Approach 1) is generally preferred due to its conciseness and often superior performance compared to explicit iteration (Approach 2). The time complexities are the same asymptotically, but the constant factors might favor the built-in replacement functions. Therefore, unless there are specific constraints or unusual characteristics of the input string that would make iteration more suitable, the replacement approach is usually the better choice.