leetcode(3)無重複字符的最長子串

無重複字符的最長子串

解題思想：滑動窗口

方法1

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int len = s.length();
        if(len == 0){
            return 0;
        }
        int begin = 0;
        int max = 1;
        String sub = null;
        int index = 0;
        for(int i=1;i<len;i++){
            sub = s.substring(begin,i);
            index = sub.indexOf(s.charAt(i));
            if(index!=-1){
               if(max<i-begin){
                   max = i-begin;
               }
               begin += index+1; 
            }
        }
        if(max<len-begin){
            max = len - begin;
        }
        return max;
    }
}

 方法2

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int len = s.length();
        if(len == 0){
            return 0;
        }
        int begin = 0;
        int max = 1;
        Integer index = 0;
        char c = 0;
        Map<Character,Integer> map = new HashMap<>();
        map.put(s.charAt(0),0);
        for(int i=1;i<len;i++){
            c = s.charAt(i);
            index = map.get(c);
            if(index!=null&&index>=begin){
               if(max<i-begin){
                   max = i-begin;
               }
               begin = index+1; 
            }
            map.put(c,i);
        }
        if(max<len-begin){
            max = len - begin;
        }
        return max;
    }
}