C-printf Parser

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题目

There is a function in C language: printf. This function allows us to print something with formatting. Like this:

printf("The result is %d.", 42);

This challenge requires you to parse the input string and extract the format placeholders like %d and %f. For example, if the input string is "The result is %d.", the parsed result is a tuple ['dec'].

Here is the mapping:

type ControlsMap = {
  c: "char";
  s: "string";
  d: "dec";
  o: "oct";
  h: "hex";
  f: "float";
  p: "pointer";
};

解答

// your answers
type ControlsMap = {
  c: "char";
  s: "string";
  d: "dec";
  o: "oct";
  h: "hex";
  f: "float";
  p: "pointer";
};

type ParsePrintFormat<
  S extends string,
  ResultArr extends string[] = []
> = S extends `${string}%${infer Letter}${infer Rest}`
  ? Letter extends keyof ControlsMap
    ? ParsePrintFormat<Rest, [...ResultArr, ControlsMap[Letter]]>
    : ParsePrintFormat<Rest, ResultArr>
  : ResultArr;