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Resolve a cd Path Against the Current Directory

MetaSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteCoding & Algorithms

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Implement simplified Unix-style cd path resolution for absolute and relative inputs containing repeated separators, dot components, and parent-directory steps. The challenge focuses on component semantics, root boundaries, empty arguments, exact normalization, and linear processing of long paths without filesystem lookups.

Resolve a cd Path Against the Current Directory

Implement path resolution for a simplified Unix-like cd command.

cwd is a normalized absolute path. argument may be absolute or relative and may contain repeated / separators, . components, and .. components. Resolving .. at the root keeps the result at the root. Return a normalized absolute path with no trailing slash unless the result is /.

Do not implement symbolic links, environment variables, ~, wildcard expansion, or filesystem existence checks.

Function Signature

def resolve_cd(cwd: str, argument: str) -> str:
 ...

Constraints

  • 1 <= len(cwd), len(argument) <= 200_000
  • cwd starts with / and is already normalized.
  • Empty components created by repeated separators are ignored; every ordinary component contains non-slash characters.
  • An empty string argument leaves the current directory unchanged. Any argument beginning with / starts from the root, so / and //// both resolve to /.

Examples

Input: cwd = "/home/alex/projects", argument = "../docs/./api"
Output: "/home/alex/docs/api"

Input: cwd = "/a/b", argument = "/x//y/../../z"
Output: "/z"

Input: cwd = "/", argument = "../../../tmp"
Output: "/tmp"