String Pattern Replacement

You are given an input string s, a pattern string pattern, and a replacement string replacement.

Return a new string where every non-overlapping occurrence of pattern in s is replaced by replacement.

Process the string from left to right. Once a match is replaced, continue scanning after the matched substring in the original input.

If pattern does not appear in s, return s unchanged. You may not use a built-in replace-all function.

Clarifications / Interview Discussion

Before implementing, clarify these rules:

• What should happen if pattern is empty?
• Are matches case-sensitive?
• Should overlapping matches be replaced? If not, which match wins?
• What should happen if replacement is empty?
• What if replacement itself contains pattern?
• Should newly inserted text be scanned again, or only the original input?
• What should happen if pattern is longer than s?

For this problem, use these assumptions:

• pattern is non-empty.
• Matching is case-sensitive.
• Only non-overlapping matches are replaced.
• The scan proceeds from left to right.
• replacement may be empty, in which case the matched pattern is deleted.
• If replacement contains pattern, do not recursively replace inside newly inserted text.

Function Signature

function replacePattern(s: string, pattern: string, replacement: string): string