字符串最长不重复字符序列

转载请注明作者与出处：franciscolv http://www.cnblogs.com/franciscolv/archive/2011/11/20/2255852.html

package SortSet;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 最长不重复子串 注意最后的时候比较i-start和最长子串的情况 以防止丢失值
 * 
 * @author franciscolv
 * 
 */
public class MaxLenSubString {

    public static void main(String[] args) {
        List<String> result = maxLenSubString("absccdfkmnok");
        for (String s : result)
            System.out.println(s);
    }

    /**
     * o(n)获取最大长度 o(n*n)构造全部结果
     * 
     * @param s
     * @return
     */
    public static List<String> maxLenSubString(String s) {
        char[] c = s.toCharArray();
        Map<Character, Integer> charMap = new HashMap<Character, Integer>();
        List<String> maxSubList = new ArrayList<String>();
        int start = 0, max = 0;
        int i = 0;
        for (; i < c.length; i++) {
            if (charMap.containsKey(c[i])) {
                int tmp = i - start;
                int pos = charMap.get(c[i]);
                if (tmp >= max) {
                    if (tmp > max)
                        maxSubList.clear();
                    /**
                     * 这里需要o(n)才能构建出子串
                     */
                    maxSubList.add(s.substring(start, i));
                    charMap.put(c[i], i);
                    max = tmp;
                } else
                    charMap.put(c[i], i);
                start = pos + 1;
            } else 
                charMap.put(c[i], i);
        }
        if (i - start >= max) {
            if (i - start > max) {
                maxSubList.clear();
                max = i - start;
            }
            maxSubList.add(s.substring(start, i));
        }
        System.out.println(max);
        return maxSubList;

    }
}