Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3. 
Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:

Input: "pwwkew"
Output: 3
Explanation: 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.

 

解题思路：利用滑动窗口来获取字符并且判断出最大的长度。

class Solution {
    public int lengthOfLongestSubstring(String s) {
        
        ArrayList a=new ArrayList();   
        if(s.length()>0)
        {
            a.add(s.charAt(0));
        int max=1;
        int left=0;
       for(int i=1;imax)
            		max=a.size();
            	}
            	else
            	{
            		a.add(s.charAt(i));
            		if(a.size()>max)
                		max=a.size();
            	}
            }
       return max; 
       }
        else 
            return 0;
       
    }
}