java算法----求最长子串

package com.dazhongdianping.interview;

import java.util.HashMap;
import java.util.Map;

/**
 * 求一个字符串中不重复字符的最长子串，如字符串"abcdefghiud",最长的不重复的子串为"abcdefghiu"
 * @author yangjianzhou
 *
 */
public class MaxSubstring {
	public static void main(String[] args) {
		longestNodupSubstring("abcdefghijhh");
	}

	/**cursor里面存放字符的在字符串中的位置
	 * lengAt[i]存放以字符string.charAt(i)结尾的最长子字符串的长度
	 * @param string
	 */
	public static void longestNodupSubstring(String string)
	{
		int len = string.length();
		if(len>0){
			Map cursor = new HashMap();
			cursor.put(string.charAt(0), 0);
			int [] lengthAt = new int[string.length()];
			lengthAt[0] =1;
			int max =0;
			for(int i = 1 ;i				char c = string.charAt(i);
				if(cursor.containsKey(c)){
					lengthAt[i] = Math.min(lengthAt[i-1]+1, i-cursor.get(c));   
				}else {
					lengthAt[i] = lengthAt[i-1]+1;
				}
				max = Math.max(max, lengthAt[i]);
				cursor.put(c, i);
			}
			for(int i=0;i				if(max == lengthAt[i]){
					System.out.println(string.substring(i-max+1, i+1));
				}
			}
		}
	}

}

运行结果：

abcdefghij