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.
Solution:
public class Solution { public String countAndSay(int n) { if (n==0) return ""; StringBuilder actual = new StringBuilder("1"); String previous; for(int i=1; i<n; i++) { previous = actual.toString(); actual = new StringBuilder(); char car = previous.charAt(0); int count = 1; for(int j=1; j<previous.length(); j++) { if(previous.charAt(j)==car) count++; else { actual.append(count); actual.append(car); car = previous.charAt(j); count = 1; } } actual.append(count); actual.append(car); } return actual.toString(); } }
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