LeetCode第3题：空字符串输入下，本地与平台输出结果不同的原因是什么？

import java.util.*;
class Solution {
    public int lengthOfLongestSubstring(String s) {
        String temp1="";
        ArrayList<String> result= new ArrayList<String>();
        for(int i=0;i<s.length();i++){
            if(i==0){
                temp1=String.valueOf(s.charAt(i));
            }
            for(int j=0;j<result.size();j++){
                int t=result.get(j).length();
                int target=0;
                if(t>target){
                    target=t;
                }
            }
        }
        return target; // 这里target初始值为0
    }
}

import java.util.*;
class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) return 0; // 处理空字符串情况

        Map<Character, Integer> charIndexMap = new HashMap<>();
        int maxLength = 0;
        int start = 0;

        for (int end = 0; end < s.length(); end++) {
            char c = s.charAt(end);
            if (charIndexMap.containsKey(c) && charIndexMap.get(c) >= start) {
                start = charIndexMap.get(c) + 1;
            }
            charIndexMap.put(c, end);
            maxLength = Math.max(maxLength, end - start + 1);
        }
        return maxLength;
    }
}