- Use one variable to store prev result.
stackis more wise.
- The description of this question is quite confusing.
- Even it’s a medium question, it’s not that hard. Don’t be terrified!
The count-and-say sequence is a sequence of digit strings defined by the recursive formula:
- countAndSay(1) = “1”
- countAndSay(n) is the way you would “say” the digit string from countAndSay(n-1), which is then converted into a different digit string.
To determine how you “say” a digit string, split it into the
minimal number of groups so that each group is a contiguous section all of the
same character. Then for each group, say the number of characters, then say the character. To convert the saying into a digit string, replace the counts with a number and concatenate every saying.
For example, the saying and conversion for digit string “
Given a positive integer n, return the nth term of the count-and-say sequence.
Input: n = 4