题目

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

解题思路

1.应该可以用分治法的，不过目前还没想到怎么合并。

2.顺序枚举主串中的所有字符，以此作为子串的最后一个字符。对于每种情况，找出最长的不重复子串。时间复杂度O(n)，空间复杂度O(n)。（√）

代码

public class Solution {
    
    public int lengthOfLongestSubstring(String s) {
        
        java.util.Hashtable<String,Integer> hashtb=new java.util.Hashtable<String,Integer>();
        int start=0;
        int max=0;
        String ch; 

        for(int i=0;i<s.length();++i){
            ch=java.lang.Character.toString(s.charAt(i));

            if(hashtb.containsKey(ch)){
                start=(hashtb.get(ch)+1)>start?(hashtb.get(ch)+1):start;
                hashtb.remove(ch);
            }   

            max=(i-start+1)>max?(i-start+1):max;
            hashtb.put(ch,i);
        }   

        return max;
    }
    
}

运行结果

3.Longest Substring Without Repeating Characters

原文：http://blog.csdn.net/hiboy_111/article/details/47715379