两指针（2）

原题：

/** * Created by gouthamvidyapradhan on 09/03/2017. * Given a string, find the length of the longest substring without repeating characters. * <p> * Examples: * <p> * Given "abcabcbb", the answer is "abc", which the length is 3. * <p> * Given "bbbbb", the answer is "b", with the length of 1. * <p> * Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring. */

答案：

public class LongestSubstringWitoutRepeats {    Set<Character> set = new HashSet<>();    /**     * Main method     *     * @param args     * @throws Exception     */    public static void main(String[] args) throws Exception {        System.out.println(new LongestSubstringWitoutRepeats().lengthOfLongestSubstring("asdfsdfsdfsdfasdfdjdjjdjjdjjjjjajsdjjdjdjjd"));    }    private int lengthOfLongestSubstring(String s) {        if (s == null || s.isEmpty()) return 0;        Map<Character, Integer> map = new HashMap<>();        int i = 0, max = Integer.MIN_VALUE;        for (int j = 0, l = s.length(); j < l; j++) {            if (map.keySet().contains(s.charAt(j))) {                i = Math.max(map.get(s.charAt(j)) + 1, i);            }            map.put(s.charAt(j), j);            max = Math.max(max, (j - i) + 1);        }        return max;    }}