Problem: Count and Say

Medium

30 min

Explore how to construct the count and say sequence by applying run-length encoding to previous strings. This lesson helps you master tracking data patterns to solve problems involving sequences, permutations, and anagrams commonly seen in coding interviews.

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 $n^{th}$ string in the count-and-say sequence.

Constraints:

$1 \leq$ n $\leq 30$

Problem: Count and Say

Medium

30 min

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).

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

Constraints:

$1 \leq$ n $\leq 30$

Problem: Count and Say

Statement

Examples

Understand the problem

Figure it out!

Try it yourself

Problem: Count and Say

Statement

Examples

Understand the problem

Figure it out!

Try it yourself