Problem
The count-and-say sequence is the sequence of integers with the first five terms as following:
1. 1 2. 11 3. 21 4. 1211 5. 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"
Analysis
This problem is about string operation
Solution
class Solution { public: string countAndSay(int n) { string num = "1"; //interatively read n times for(int i=1; i<n; i++){ num = helper(num); } return num; } //helper function for reading a number string helper(string num){ stringstream nextStr; char last = num[0]; int count = 1; for(int i=1; i<num.size(); i++){ if(num[i] == last){ count++; }else{ nextStr<<count<<last; last = num[i]; count = 1; } } nextStr<<count<<last; return nextStr.str(); } };