java 代码

class Solution {
    public int longestSubstringWithoutDuplication(String s) {
        int len = s.length();
        if(len == 0 || len == 1) return len;
        //定义一个数组，长度位26。用于存储a-z最后一次出现的位置
        int[] array = new int[]{-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1};
        int frist = 0;
        int second = 1;
        int max = 1;
        while(frist < len){
            int fristchar = s.charAt(frist)-97;
            array[fristchar] = frist;
            while(second < len){
                int secondchar = s.charAt(second)-97;
                if(array[secondchar] != -1){
                    frist = frist<=array[secondchar]? array[secondchar]+ 1:frist;
                }
                array[secondchar] = second;
                if((second-frist + 1) > max) max = second-frist + 1;
                second++;
            }
            frist++;
        }
        return max;
    }

}