package class020;

public class Code03_LongestNoRepeatSubstring {

	/*
	 * 给定一个只由小写字母（a~z）组成的字符串str， 返回其中最长无重复字符的子串长度
	 * 
	 */

	public static int lnrs1(String s) {
		if (s == null || s.length() == 0) {
			return 0;
		}
		char[] str = s.toCharArray();
		int N = str.length;
		int max = 0;
		for (int i = 0; i < N; i++) {
			boolean[] set = new boolean[26];
			for (int j = i; j < N; j++) {
				if (set[str[j] - 'a']) {
					break;
				}
				set[str[j] - 'a'] = true;
				max = Math.max(max, j - i + 1);
			}
		}
		return max;
	}

	public static int lnrs2(String s) {
		if (s == null || s.length() == 0) {
			return 0;
		}
		char[] str = s.toCharArray();
		int N = str.length;
		int[] last = new int[26];
		for (int i = 0; i < 26; i++) {
			last[i] = -1;
		}
		last[str[0] - 'a'] = 0;
		int max = 1;
		int preMaxLen = 1;
		for (int i = 1; i < N; i++) {
			preMaxLen = Math.min(i - last[str[i] - 'a'], preMaxLen + 1);
			max = Math.max(max, preMaxLen);
			last[str[i] - 'a'] = i;
		}
		return max;
	}

	// for test
	public static String getRandomString(int possibilities, int maxSize) {
		char[] ans = new char[(int) (Math.random() * maxSize) + 1];
		for (int i = 0; i < ans.length; i++) {
			ans[i] = (char) ((int) (Math.random() * possibilities) + 'a');
		}
		return String.valueOf(ans);
	}

	public static void main(String[] args) {
		int possibilities = 26;
		int strMaxSize = 100;
		int testTimes = 1000000;
		System.out.println("test begin, test time : " + testTimes);
		for (int i = 0; i < testTimes; i++) {
			String str = getRandomString(possibilities, strMaxSize);
			int ans1 = lnrs1(str);
			int ans2 = lnrs2(str);
			if (ans1 != ans2) {
				System.out.println("Oops!");
			}
		}
		System.out.println("test finish");

	}

}