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Problem · String

Reversible Run-Length Encoding

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Problem statement

Process ENCODE and DECODE rows over printable ASCII strings. Return one transformed string per row.

Encode every maximal run as count#asciiCode;, where count is the positive decimal run length and asciiCode is the character's decimal ASCII code. Concatenate the run records without separators beyond the shown # and ;. The empty string encodes to the empty string.

A row is either ["ENCODE", plainText] or ["DECODE", encodedText]. Every decode input is a valid string produced by this encoding.

Function

transformRuns(operations: String[][]) → String[]

Examples

Example 1

operations = [["ENCODE","aa11!!"],["DECODE","2#97;2#49;2#33;"],["ENCODE","A;#"]]return = ["2#97;2#49;2#33;","aa11!!","1#65;1#59;1#35;"]

Digits and delimiter characters are represented by their ASCII codes, so decoding is unambiguous.

Example 2

operations = [["ENCODE",""],["DECODE",""],["ENCODE","$$$$"]]return = ["","","4#36;"]

Empty text remains empty, while four dollar signs form one run with ASCII code 36.

Constraints

  • 1 <= operations.length <= 100000.
  • Plain text has at most 100000 printable ASCII characters.
  • The total decoded length across the batch is at most 1000000.
  • Every DECODE input is a valid encoding generated by the documented format.
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public String[] transformRuns(String[][] operations) {
    // Write your code here.
}
operations[["ENCODE","aa11!!"],["DECODE","2#97;2#49;2#33;"],["ENCODE","A;#"]]
expected["2#97;2#49;2#33;", "aa11!!", "1#65;1#59;1#35;"]
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