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package class020;
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public class Code03_LongestNoRepeatSubstring {
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/*
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* 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
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*
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*/
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public static int lnrs1(String s) {
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if (s == null || s.length() == 0) {
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return 0;
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}
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char[] str = s.toCharArray();
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int N = str.length;
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int max = 0;
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for (int i = 0; i < N; i++) {
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boolean[] set = new boolean[26];
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for (int j = i; j < N; j++) {
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if (set[str[j] - 'a']) {
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break;
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}
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set[str[j] - 'a'] = true;
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max = Math.max(max, j - i + 1);
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}
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}
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return max;
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}
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public static int lnrs2(String s) {
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if (s == null || s.length() == 0) {
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return 0;
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}
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char[] str = s.toCharArray();
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int N = str.length;
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int[] last = new int[26];
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for (int i = 0; i < 26; i++) {
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last[i] = -1;
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}
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last[str[0] - 'a'] = 0;
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int max = 1;
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int preMaxLen = 1;
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for (int i = 1; i < N; i++) {
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preMaxLen = Math.min(i - last[str[i] - 'a'], preMaxLen + 1);
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max = Math.max(max, preMaxLen);
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last[str[i] - 'a'] = i;
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}
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return max;
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}
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// for test
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public static String getRandomString(int possibilities, int maxSize) {
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char[] ans = new char[(int) (Math.random() * maxSize) + 1];
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for (int i = 0; i < ans.length; i++) {
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ans[i] = (char) ((int) (Math.random() * possibilities) + 'a');
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}
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return String.valueOf(ans);
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}
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public static void main(String[] args) {
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int possibilities = 26;
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int strMaxSize = 100;
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int testTimes = 1000000;
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System.out.println("test begin, test time : " + testTimes);
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for (int i = 0; i < testTimes; i++) {
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String str = getRandomString(possibilities, strMaxSize);
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int ans1 = lnrs1(str);
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int ans2 = lnrs2(str);
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if (ans1 != ans2) {
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System.out.println("Oops!");
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}
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}
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System.out.println("test finish");
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}
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}
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