【Problem】Count and Say

 1 public class Solution {
 2     public String countAndSay(int n) {
 3         
 4         if ( n == 1 ) {
 5             return "1";
 6         } else {
 7             
 8             char current;    // the current char
 9             int count;       // the count of the current char
10             String result = new String("1");  // the result
11             int length = result.length();     // the length of the result string
12             StringBuilder strBuilder = new StringBuilder(); // store the current result
13             
14             int i = 0;
15             while ( n > 1 ) {
16                 for ( i = 0; i < length; i++ ) {
17                     current = result.charAt(i);
18                     count = 1;
19                     // while the next char is the same as the current char
20                     while ( (i+1 < length) &&
21                             (result.charAt(i+1) ==  current) ) {
22                         count++;
23                         i++;
24                     }
25                     // add the char and its count to the current result
26                     strBuilder.append(count).append(current);
27                 }
28                 // update the result and its length, and clear the content of strBuilder for the next loop
29                 result = strBuilder.toString();
30                 length = result.length();
31                 strBuilder = new StringBuilder();
32                 n--;
33             }
34 
35             return result;
36         }
37     }
38 }