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
Constraints:
n
The count and say problem generates a sequence of strings, where each term describes the previous one. Starting from “1”, every next term is built by counting consecutive identical digits and writing the count followed by the digit.
To solve this efficiently, we use the knowing what to track pattern. While scanning a string, we only need to track the current digit and the number of consecutive occurrences. This allows us to build each next string in a single pass, without extra data structures or redundant work.
The solution starts from the first string and repeatedly constructs the next string until the required position is reached. For each step, the previous string is read from left to right. Consecutive identical digits are grouped, and each group is converted into a short description consisting of the group’s size and the digit itself. This process is repeated iteratively to ensure efficiency and clarity.
Here’s the detailed algorithm that we’ll use to solve the given problem:
Initialize result as “1” because the first element of the count and say sequence is always “1”.
Next, iterate over the input array n starting from the second index to
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
Constraints:
n
The count and say problem generates a sequence of strings, where each term describes the previous one. Starting from “1”, every next term is built by counting consecutive identical digits and writing the count followed by the digit.
To solve this efficiently, we use the knowing what to track pattern. While scanning a string, we only need to track the current digit and the number of consecutive occurrences. This allows us to build each next string in a single pass, without extra data structures or redundant work.
The solution starts from the first string and repeatedly constructs the next string until the required position is reached. For each step, the previous string is read from left to right. Consecutive identical digits are grouped, and each group is converted into a short description consisting of the group’s size and the digit itself. This process is repeated iteratively to ensure efficiency and clarity.
Here’s the detailed algorithm that we’ll use to solve the given problem:
Initialize result as “1” because the first element of the count and say sequence is always “1”.
Next, iterate over the input array n starting from the second index to