package test.strings;

import java.util.Random;

import strings.ZFunction;

public class ZFunctionTest {

// random tests

public static void main(String[] args) {

Random rnd = new Random(1);

for (int step = 0; step < 10_000; step++) {

String s = getRandomString(rnd, 100);

String pattern = getRandomString(rnd, 5);

int pos1 = find(s, pattern);

int pos2 = s.indexOf(pattern);

if (pos1 != pos2)

throw new RuntimeException();

}

}

static int find(String s, String pattern) {

int[] z = ZFunction.zFunction(pattern + "\0" + s);

for (int i = pattern.length() + 1; i < z.length; i++)

if (z[i] == pattern.length())

return i - pattern.length() - 1;

return -1;

}

static String getRandomString(Random rnd, int maxlen) {

int n = rnd.nextInt(maxlen) + 1;

char[] s = new char[n];

for (int i = 0; i < n; i++) s[i] = (char) ('a' + rnd.nextInt(3));

return new String(s);

}

}