3. 无重复字符的最长子串

import java.util.HashSet;
import java.util.Set;
 
public class Q3 {
    public int lengthOfLongestSubstring(String s) {
        int maxLength = 0;
 
        //滑动窗口法
        Set<Character> occ = new HashSet<>();
        int rk = -1;//右指针
        for (int i = 0; i < s.length(); i++) {
            if (i != 0) {
                occ.remove(s.charAt(i-1));
            }
 
            //右移 右指针，直到集合出现重复字符
            while (rk+1 < s.length() && !occ.contains(s.charAt(rk+1))) {
                occ.add(s.charAt(rk+1));
                ++rk;
            }
            //更新maxLength
            if ((rk-i+1) > maxLength)
                maxLength = rk-i+1;
 
        }
        // end for
 
        return maxLength;
    }
}