Problem
The count-and-say sequence is the sequence of integers with the first five terms as following:
- 1
- 11
- 21
- 1211
- 111221
1 is read off as “one 1” or 11. 11 is read off as “two 1s” or 21. 21 is read off as “one 2, then one 1” or 1211. Given an integer n, generate the nth term of the count-and-say sequence.
Note: Each term of the sequence of integers will be represented as a string.
Example 1:
Input: 1 Output: “1” Example 2:
Input: 4 Output: “1211”
题目的意思就是反复的计算字符中,从左向右,每种字符的数量和值。
1 -> 1个1,即11。
11 -> 2个1,即21。
21 -> 1个2,1个1,即1211。以此类推。