#1678

Easy

auto_awesomeString-driven solution strategy

LeetCode Problem Workspace

Goal Parser Interpretation

Interpret the Goal Parser's output by analyzing a command string containing 'G', '()', and '(al)' patterns.

Problem Statement

You are given a string command consisting of the characters 'G', '()', and/or '(al)'. Your task is to return the Goal Parser's interpretation of this command. The character 'G' is interpreted as 'G', '()' as 'o', and '(al)' as 'al'. These interpreted characters are concatenated in the order they appear in the string.

For example, in the command 'G()(al)', 'G' becomes 'G', '()' becomes 'o', and '(al)' becomes 'al', so the final output would be 'Goal'.

Examples

Example 1

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

Output: "Goal"

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 details omitted.

Example 3

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

Output: "alGalooG"

Example details omitted.

Constraints

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

Solution Approach

String-driven solution

Iterate over the input string character by character. When encountering 'G', directly append 'G' to the result. For '()', append 'o' and for '(al)', append 'al'. A simple loop through the string will help identify these patterns and build the result string.

Efficient Pattern Matching

To determine whether the next substring is '()', '(al)', or 'G', you only need to check the first two characters. This makes the approach both time-efficient and easy to implement, as each segment can be processed with constant checks.

Optimized Memory Usage

Since the output string can be built in-place by appending characters directly, you can minimize space usage by avoiding unnecessary data structures. A simple string accumulation approach will ensure memory efficiency.

Complexity Analysis

Metric	Value
Time	Depends on the final approach
Space	Depends on the final approach

The time complexity of this solution is O(n), where n is the length of the input string. This is because each character is processed once. The space complexity is O(n) due to the storage of the final interpreted string.

What Interviewers Usually Probe

Candidate shows an understanding of string pattern recognition.
The approach demonstrates efficient handling of string manipulation.
Candidate is able to optimize for both time and space complexity.

Common Pitfalls or Variants

Common pitfalls

Misidentifying the characters '()' and '(al)' could lead to incorrect interpretation of the command.
Failing to handle the case where multiple '()' or '(al)' patterns appear consecutively.
Inefficient solutions that unnecessarily process characters multiple times or use extra space.

Follow-up variants

Handle more complex input where the patterns appear in mixed order.
Allow modifications where additional patterns (like '[]') are introduced.
Optimize for very long strings while maintaining performance.

FAQ

How can I solve the Goal Parser Interpretation problem efficiently?

The efficient way to solve this problem is by iterating through the command string and using simple checks to identify and process the 'G', '()', and '(al)' patterns.

What is the expected time complexity for this problem?

The time complexity is O(n), where n is the length of the command string, since each character is processed only once.

Can this problem be solved with constant space?

Yes, the problem can be solved with constant space by directly concatenating the interpreted segments into a result string.

How do I handle multiple consecutive '()' and '(al)' patterns?

Simply continue iterating through the string, treating each '()', '(al)', and 'G' independently and appending the appropriate character or string to the result.

What should I do if the problem adds new patterns?

You can extend the solution by adding more checks to handle new patterns in the same manner as '()', '(al)', and 'G'.

terminal

Solution

Solution 1: String Replacement

According to the problem, we only need to replace `"()"` with `'o'` and `"(al)"` with `"al"` in the string `command`.

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class Solution:
    def interpret(self, command: str) -> str:
        return command.replace('()', 'o').replace('(al)', 'al')

Solution 2: String Iteration

We can also iterate over the string `command`. For each character $c$:

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class Solution:
    def interpret(self, command: str) -> str:
        return command.replace('()', 'o').replace('(al)', 'al')

Continue Practicing

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