力扣-3题（Java）-滑动窗口+哈希

一时失言乱红尘 2023-01-19 04:39 14阅读 0赞

题目链接：[https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/][https_leetcode-cn.com_problems_longest-substring-without-repeating-characters]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]

class Solution {
        
        public int lengthOfLongestSubstring(String s) {
        
            int l=0,r=-1;//滑动窗口的左右边界
            int maxlen=0,count;
            HashMap<Character,Integer> hashmap=new HashMap<Character,Integer>();
    
            while(l<s.length()){
        
                //如果右边界可能产生重复，则不拓展右边界，而缩短左边界
                if(r+1<s.length()&&(count=hashmap.getOrDefault(s.charAt(r+1),0))==0){
        
                    if(count==0){
        
                        hashmap.put(s.charAt(r+1),count+1);
                        r++;
                    }  
                }
                else {
        
                    count=hashmap.get(s.charAt(l));
                    hashmap.put(s.charAt(l),count-1);
                    l++;
                }
    
                maxlen=Math.max(maxlen,r-l+1);
            }
    
            return maxlen;
        }
    }

[https_leetcode-cn.com_problems_longest-substring-without-repeating-characters]: https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20221021/fd579eecc3574acaaba207758f40f8e7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]: /images/20221021/cdc3c24725da4c7096ae95d64952e280.png