代码来查找最长的唯一K字符子字符串，不适用于所有输入 [英] code to find longest substring with unique K characters not working for all inputs

问题描述

给出一个字符串 aabbcdeeeeggi并且k = 3，代码应找到最长的子字符串，最多包含k个唯一字符。对于上述输入，它应该是 deeeeggi。

Given a String, ""aabbcdeeeeggi" and k=3, the code should find longest substring with maximum of k unique characters. For the above input, it should be "deeeeggi".

这里是一个优雅的O（n） Python中的问题的解决方案。我正在Java中实现，但没有获得所有输入的期望输出。

Here is an elegant O(n) solution for the problem in Python. I am implementing in Java. but I am not getting the desired output for all the inputs.

public class SubStringWithKUniqueCharacters {

    public static void main(String[] args){

        System.out.println(longestSubStringWithUniqueK("aabbcdeeeeggi", 3));
        System.out.println(longestSubStringWithUniqueK("aabbcdeeeeggi", 2));
    }

    public static String longestSubStringWithUniqueK(String input, int k){
        int len = input.length();
        Set<Character> unique = new HashSet<>();

        int i = 0;
        int j = 0;
        int count = 0;
        int maxStartIndex = 0;
        int maxEndIndex  = 0;
        int maxLen = 0;
        char[] inputArr = input.toCharArray();

        while (i<len){

            if (count==k && j -i > maxLen){
                maxStartIndex = i;
                maxEndIndex = j;
                maxLen = maxEndIndex - maxStartIndex;
            }
             if (count<k && j<len){
                if (unique.add(inputArr[j])){
                    count++;
                }
                j++;
            }
            else {
                if (unique.remove(inputArr[i])){
                    count--;
                }
                i++;
            }
        }
         return input.substring(maxStartIndex,maxEndIndex);
    }
}

这是输出：

eeeeggi //correct output
eeeggi //incorrect output

我无法捕获错误所在。任何帮助将非常感激。
谢谢

I am not able to capture where the bug is. Any help would be much appreciated. Thanks

推荐答案

您的实现无法按预期方式运行，原因是原始的python解决方案存在错误。我对您的代码做了一些修改。希望现在一切正常：

Your implementation does not work the way as expected, is because the original python solution has bug. I made some modifications to your code. Hope it's now all right:

public class SubStringWithKUniqueCharacters {

    public static void main(String[] args){

        System.out.println(longestSubStringWithUniqueK("aabbcdeeeeggi", 3));
        System.out.println(longestSubStringWithUniqueK("aabbcdeeeeggi", 2));
    }

    public static String longestSubStringWithUniqueK(String input, int k){
        int len = input.length();
        Set<Character> unique = new HashSet<>();

        int i = 0;
        int j = 0;
        int count = 0;
        int maxStartIndex = 0;
        int maxEndIndex  = 0;
        int maxLen = 0;
        char[] inputArr = input.toCharArray();

        while (i<len){

            if (count==k && j -i > maxLen){
                maxStartIndex = i;
                maxEndIndex = j;
                maxLen = maxEndIndex - maxStartIndex;
            }
            // 1. if we reach the end of the string, we're done.
            if (j + 1 > len){
                break;
            }
            // 2. changed to count <= k here
            else if (count<= k && j<len){
                if (unique.add(inputArr[j])){
                    count++;
                }
                j++;
            }
            else {                          
                if (unique.remove(inputArr[i])){
                    // 3. remove all consecutive chars of the same value
                    char c = inputArr[i];  // save as temp char
                    while (inputArr[i] == c)
                    {
                        i++;
                    }
                    count--;                          
                }                
            }
        }
         return input.substring(maxStartIndex,maxEndIndex);
    }
}

现在的输出为：

deeeegg
eeeegg

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