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Grokking the Coding Interview Patterns in C++

Solution: Count and Say

Explore how to apply the knowing what to track pattern to solve the count and say sequence efficiently. Understand run-length encoding and how to track consecutive characters to build each term in the sequence. This lesson guides you through an iterative approach that enhances clarity and performance for coding interview problems.

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Statement

The “count and say” is a sequence of strings built by describing the previous string:

  • The sequence starts with countAndSay(1) = “1”

  • For n > 1, countAndSay(n) is created by run-length encoding the string countAndSay(n - 1).

Run-length encoding (RLE) works by grouping identical consecutive characters and replacing each group with the count of characters followed by the character itself. For example, the string “15224” is read as: one 1, one 5, two 2s, and one 4, producing “11152214”.

Given a positive integer n, return the nthn^{th} string in the count-and-say sequence.

Constraints:

  • ...