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.
public class Solution { public String countAndSay(int n) { // Start typing your Java solution below // DO NOT write main() function String temp = String.valueOf(1); for(int i = 0 ; i < n-1 ; i++){ temp = cs(temp);//when update string make sure oldString = function(oldString) } return temp; } public String cs(String temp){ char[] chars= temp.toCharArray(); StringBuilder sb = new StringBuilder(); for(int i = 0 ; i < chars.length; i++){ int count = 1; while( i + 1 < chars.length && chars[i+1] == chars[i]){ count++; i++; //skip duplicated one } sb.append(String.valueOf(count)+String.valueOf(chars[i]));//do count and say } return sb.toString(); } }
learned: String.valueOf(1) return 1
public class Solution { public String countAndSay(int n) { if(n< 0 )return null; StringBuilder res = new StringBuilder("1"); while(n-->1){ StringBuilder temp = new StringBuilder(); int count = 1; for(int i = 1 ; i < res.length() ; i++){ if(res.charAt(i) == res.charAt(i-1)){ count++; } else{ temp.append(count); temp.append(res.charAt(i-1)); count = 1; } } temp.append(count); temp.append(res.charAt(res.length()-1)); res = temp; } return res.toString(); } }