LeetCode Question 3: What is the reason why the local and platform output results are different when inputting an empty string?

LeetCode Question 3: Analysis of the difference between local and platform output results under empty string input

When solving LeetCode Question 3 "The longest substring without duplicate characters", some developers may encounter situations where the output results of the local environment (such as Visual Studio) are inconsistent with the LeetCode platform. This article will analyze a specific case: when the input is an empty string "", the LeetCode platform outputs 0, and the local environment outputs 1.

The problem code snippet is as follows:

 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 if temp1="String.valueOf(s.charAt(i));" for j="0;j<result.size();j" int t="result.get(j).length();" target="0;"> target){
                    target=t;
                }
            }
        }
        return target; // Here the initial value of target is 0
    }
}</s.length></string></string>

When the input is an empty string, the LeetCode platform returns 0, while the local environment returns 1. The reason is a code logic flaw: after the loop ends, the temp1 variable may contain a string that is not added to the result list. When the input is an empty string, the loop will not be executed, temp1 remains as an empty string, and result list is also empty. Therefore, the value of target is always its initial value 0, which is consistent with the LeetCode platform output. The local environment outputs 1, most likely because the local test environment is different from the LeetCode platform environment, or the local test case is different from the LeetCode platform test case, and there may be other code or environment factors not shown.

The root cause is code logic errors, not environment differences. This code simply does not correctly calculate the length of the longest non-repeat substring. It just loops through the string and uses target variable incorrectly.

Corrected code: This function needs to be completely rewrite to correctly calculate the longest non-repetitive substring length. Here is a correct Java implementation:

 import java.util.*;
class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) return 0; // Handle empty strings Map<character integer> charIndexMap = new HashMap();
        int maxLength = 0;
        int start = 0;

        for (int end = 0; end = start) {
                start = charIndexMap.get(c) 1;
            }
            charIndexMap.put(c, end);
            maxLength = Math.max(maxLength, end - start 1);
        }
        return maxLength;
    }
}</character>

This corrected code uses sliding window technology to correctly process various inputs, including empty strings, to ensure consistent and correct results are obtained in all environments. The logic error of the original code is the root cause of inconsistency in local and platform results, not environmental differences.

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