Build a tiny version of the Unix grep command. Given a list of lines and a search pattern, return all lines that contain pattern as a substring (case-sensitive), joined by newline characters (\n).
Function signature:
def grep(self, lines: List[str], pattern: str) -> str:
Example:
Input: pattern = "err" lines = ["error: foo", "warning", "another error", "ok"] Output: "error: foo\nanother error" When printed: error: foo another error
If no lines match, return the empty string "".
Note: real grep treats the pattern as a regular expression by default (grep -F matches plain text). Here the pattern is always plain text: just look for it literally, so characters such as . or * mean nothing special.
Iterate over the lines, keep the ones where
pattern in line is true, then join with "\n".
The full solution:
class Solution:
def grep(self, lines, pattern):
result = []
for line in lines:
if pattern in line:
result.append(line)
return "\n".join(result)
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