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This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Oracle.

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This question is commonly asked for Software Engineer candidates at Oracle during technical interviews.

Compute letter frequencies from encoded string

Quick Overview

This question evaluates proficiency in string parsing and frequency aggregation, specifically handling mixed-length encodings, tokenization of digits and '#' markers, and parsing numeric repetition counts while respecting linear-time and constant-space constraints.

Problem

You are given an encoded string s representing a string of lowercase English letters (a–z). The encoding follows these rules:

Letters a to i are encoded as digits 1 to 9 .
- a -> "1" , b -> "2" , …, i -> "9"
Letters j to z are encoded as two digits followed by # .
- j -> "10#" , k -> "11#" , …, z -> "26#"
If a letter repeats consecutively k >= 2 times, the repetition is encoded by appending "(k)" immediately after that letter’s code.
- Example: "aa" -> "1(2)" , "ccc" -> "3(3)" , "jj" -> "10#(2)"

Task

Return an integer array counts of length 26, where counts[0] is the number of 'a' characters in the decoded string, counts[1] is the number of 'b', …, and counts[25] is the number of 'z'.

Examples

s = "1226#24#" decodes to "abzx" .
s = "1(2)23(3)" decodes to "aabccc" .
s = "2110#(2)" decodes to "bajj" .
s = "23#(2)24#25#26#23#(3)" decodes to "wwxyzwww" .

Input/Output

Input: a string s consisting of digits, # , ( , and ) that follows the encoding rules above.
Output: an array of 26 integers with letter frequencies.

Notes / Constraints (reasonable interview assumptions)

s is validly encoded.
Counts in parentheses can be multiple digits (e.g., (12) ).
Aim for O(|s|) time and O(1) extra space (excluding the output array).

Quick Overview

Problem

You are given an encoded string s representing a string of lowercase English letters (a–z). The encoding follows these rules:

Letters a to i are encoded as digits 1 to 9 .

a -> "1" , b -> "2" , …, i -> "9"

Letters j to z are encoded as two digits followed by # .

j -> "10#" , k -> "11#" , …, z -> "26#"

If a letter repeats consecutively k >= 2 times, the repetition is encoded by appending "(k)" immediately after that letter’s code.

Example: "aa" -> "1(2)" , "ccc" -> "3(3)" , "jj" -> "10#(2)"

Task

Examples

s = "1226#24#" decodes to "abzx" .

s = "1(2)23(3)" decodes to "aabccc" .

s = "2110#(2)" decodes to "bajj" .

s = "23#(2)24#25#26#23#(3)" decodes to "wwxyzwww" .

Input/Output

Input: a string s consisting of digits, # , ( , and ) that follows the encoding rules above.

Output: an array of 26 integers with letter frequencies.

Notes / Constraints (reasonable interview assumptions)

s is validly encoded.

Counts in parentheses can be multiple digits (e.g., (12) ).

Aim for O(|s|) time and O(1) extra space (excluding the output array).

Compute letter frequencies from encoded string

Quick Overview

Problem

Task

Examples

Input/Output

Notes / Constraints (reasonable interview assumptions)

Submit Your Answer

Compute letter frequencies from encoded string

Quick Overview

Problem

Task

Examples

Input/Output

Notes / Constraints (reasonable interview assumptions)

Submit Your Answer