LeetCode 37 Count and Say

Posted 2020-09-14 yjbjingcha

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) {
		if (n == 0)
			return "";
		StringBuffer sb = new StringBuffer("1");
		StringBuffer tempSB = new StringBuffer();

		for (int i = 1; i < n; i++) {
			int counter = 1;
			char tempChar = sb.charAt(0);
			for (int j = 1; j < sb.length(); j++) {
				if (sb.charAt(j) == tempChar)
					counter++;
				else {
					tempSB.append(""+counter + tempChar);
					tempChar = sb.charAt(j);
					counter = 1;
				}
			}
			tempSB.append(""+counter + tempChar);
			sb.delete(0, sb.length());
			sb.append(tempSB);
			tempSB.delete(0, tempSB.length());
		}
		return sb.toString();
	}
}

或者

	public String countAndSay(int n) {
		if (n == 0) return "";
		StringBuffer sb = new StringBuffer("1");
		StringBuffer tempSB = new StringBuffer();

		for (int i = 1; i < n; i++) {
			int counter = 1;
			char tempChar = sb.charAt(0);
			for (int j = 1; j < sb.length(); j++) {
				if (sb.charAt(j) == tempChar)
					counter++;
				else {
					tempSB.append(Integer.toString(counter)+ tempChar);
					tempChar = sb.charAt(j);
					counter = 1;
				}
			}
			tempSB.append(Integer.toString(counter)+ tempChar);
			sb.delete(0, sb.length());
			sb.append(tempSB);
			tempSB.delete(0, tempSB.length());
		}
		return sb.toString();
	}