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.
一刷
題解：
題意是n=1時輸出字符串1；n=2時，數上次字符串中的數值個數，因為上次字符串有1個1，所以輸出11；n=3時，由于上次字符是11，有2個1，所以輸出21；n=4時，由于上次字符串是21，有1個2和1個1，所以輸出1211。依次類推，寫個countAndSay(n)函數返回字符串。
public class Solution {
public String countAndSay(int n) {
if(n<=0) return "";
StringBuilder sb = new StringBuilder();
String s = "1";
while(n>1){
int count = 1;
char lastChar = s.charAt(0);
for(int i=1; i<s.length(); i++){
if(s.charAt(i) == lastChar) count++;
else{
sb.append(count).append(lastChar);
count = 1;
lastChar = s.charAt(i);
}
}
sb.append(count).append(lastChar);
s = sb.toString();
sb.setLength(0);
n--;
}
return s;
}
}
