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// Source : https://leetcode.com/problems/count-and-say/description/

// Author : Tianming Cao

// Date : 2018-02-11

/**********************************************************************************

*

* 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.

*

* Example 1:

*

* Input: 1

* Output: "1"

*

* Example 2:

*

* Input: 4

* Output: "1211"

*

**********************************************************************************/

package countAndSay;

public class CountAndSay {

public String nextString(String str) {

StringBuilder next = new StringBuilder();

int len = str.length();

int i = 0;

while (i < len) {

int j = i;

int count = 0;

char currentNumber = str.charAt(i);

while (j < len && str.charAt(j) == currentNumber) {

j++;

count++;

}

next.append(count).append(currentNumber);

i = j;

}

return next.toString();

}

public String countAndSay(int n) {

if (n <= 1) {

return "1";

} else {

String p = "1";

for (int i = 2; i <= n; i++) {

String next = nextString(p);

p = next;

}

return p;

}

}

}