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Leetcode Problem 1678: 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 the command as follows:

• “G” -> “G”
• ”()” -> “o”
• “(al)” -> “al”

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

Example:

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

Clarifying Questions

Before diving into the code, let’s clarify a few points:

1. Input Constraints:
   • What is the length range of the input string? (This will help determine if efficiency is a concern)
   • Is the input guaranteed to be valid according to the rules specified?
2. Output Constraints:
   • Should we handle case sensitivity?

For now, we’ll assume:

• Input string command length is between 1 and 100.
• The input is always a valid command according to the problem’s specifications.
• Case sensitivity is handled as specified (i.e., “G” is different from “g”).

Strategy

• We will iterate through the string command.
• When we encounter a “G”, it directly interprets as “G”.
• When we encounter “()”, it interprets as “o”.
• When we encounter “(al)”, it interprets as “al”.
• We can use string manipulation to achieve this.

Code

def interpret(command: str) -> str:
    # Initialize an empty result string
    result = ""
    
    i = 0
    while i < len(command):
        if command[i] == 'G':
            result += 'G'
            i += 1
        elif command[i:i+2] == '()':
            result += 'o'
            i += 2
        elif command[i:i+4] == '(al)':
            result += 'al'
            i += 4
    
    return result

# Example usage:
print(interpret("G()(al)"))
print(interpret("G()()()()(al)"))
print(interpret("(al)G(al)()()G"))

Time Complexity

The time complexity of this solution is O(n), where n is the length of the input string command. This is because we are scanning through the string once and processing sections of it in constant time.

Space Complexity

The space complexity is also O(n) since we create a new result string whose size could be up to the length of the input string command.

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