FastPrep
Problem · String

Template Variable Expansion

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Problem statement

You are given key-value mappings and a source string. Any substring inside a pair of percent signs, such as %key%, should be treated as a key and replaced by its mapped value.

A mapped value may itself contain another key placeholder, so replacements may need to be resolved recursively.

If a referenced key is missing, or if resolving placeholders finds a cycle, return "ERROR".

Function

expandTemplate(mappings: String[][], source: String) → String

Examples

Example 1

mappings = [["x","%y%/home"],["y","user"]]source = "/%x%/docs"return = "/user/home/docs"

%x% expands to %y%/home, and %y% expands to user.

The source shared the rule but did not include this exact sample. FastPrep added this small example so the behavior can be checked directly.

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public String expandTemplate(String[][] mappings, String source) {
  // write your code here
}
mappings[["x","%y%/home"],["y","user"]]
source"/%x%/docs"
expected"/user/home/docs"
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