Title: Count and Say Source: leetcode.com
The count-and-say sequence is the sequence of integers beginning as follows:
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 sequence.
Note: The sequence of integers will be represented as a string.
Java solution
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/* https://leetcode.com/problems/count-and-say/ */ public class CountAndSay { public String countAndSay(int n) { String num = 1+""; for(int i=1;i<n;i++) { num = helper(num); } return num; } public String helper(String num) { String s=""; int count = 1; char prevChar = num.charAt(0); for(int i=1;i<num.length();i++) { if(num.charAt(i)==prevChar) { ++count; } else { s += count+""+prevChar; prevChar = num.charAt(i); count = 1; } } s+=count+""+prevChar; return s; } public static void main(String args[]) { CountAndSay cs = new CountAndSay(); System.out.println(cs.countAndSay(1)); } } |