Remove Comments — LeetCode 722 Python Solution

The problem

Given a C++ program, remove comments from it. The program source is an array of strings source where source[i] is the ith line of the source code.

Example

Input

source = ["/*Test program */", "int main()", "{ ", " // variable declaration ", "int a, b, c;", "/* This is a test", " multiline ", " comment for ", " testing */", "a = b + c;", "}"]

Output

["int main()","{ "," ","int a, b, c;","a = b + c;","}"]

Explanation

The line by line code is visualized as below:

Python solution

class Solution:
    def removeComments(self, source: List[str]) -> List[str]:
        ans = []
        t = []
        block_comment = False
        for s in source:
            i, m = 0, len(s)
            while i < m:
                if block_comment:
                    if i + 1 < m and s[i : i + 2] == "*/":
                        block_comment = False
                        i += 1
                else:
                    if i + 1 < m and s[i : i + 2] == "/*":
                        block_comment = True
                        i += 1
                    elif i + 1 < m and s[i : i + 2] == "//":
                        break
                    else:
                        t.append(s[i])
                i += 1
            if not block_comment and t:
                ans.append("".join(t))
                t.clear()
        return ans

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 722. Remove Comments is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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