LyndonDecomposition.java

package Strings;
import java.util.*;

public class LyndonDecomposition {

	public static String minCyclicShift(String a) {
		char[] s = (a + a).toCharArray();
		int n = s.length;
		int res = 0;
		for (int i = 0; i < n / 2; ) {
			res = i;
			int j = i + 1, k = i;
			while (j < n && s[k] <= s[j]) {
				if (s[k] < s[j])
					k = i;
				else
					++k;
				++j;
			}
			while (i <= k) i += j - k;
		}
		return new String(s, res, n / 2);
	}

	public static String[] decompose(String s) {
		List<String> res = new ArrayList<>();
		char[] a = s.toCharArray();
		int n = a.length;
		int i = 0;
		while (i < n) {
			int j = i + 1, k = i;
			while (j < n && a[k] <= a[j]) {
				if (a[k] < a[j])
					k = i;
				else
					++k;
				++j;
			}
			while (i <= k) {
				res.add(s.substring(i, i + j - k));
				i += j - k;
			}
		}
		return res.toArray(new String[0]);
	}

	public static void main(String[] args) {
		String s = "bara";
		String[] decompose = decompose(s);
		System.out.println(Arrays.toString(decompose));
		System.out.println(minCyclicShift(s));
	}
}