来自CodingBat的maxBlock替代解决方案

Question

从codingBat解决这个问题

给定一个字符串，返回字符串中最大“块”的长度。块是相同的相邻字符的运行。

maxBlock（“hoopla”）→ 2
maxBlock（“abbccddbbbxx”）→ 3
maxBlock（“”）→ 0

我试图解决它使用一个为循环如下：

public int maxBlock(String str) {
  int maxCounter=1;
  int counter=1;
  if(str.length()==0)
  {
    return 0;
  }  
  for(int i=0;i<str.length()-1;i++)
  {
    if(str.substring(i,i+1).equals(str.substring(i+1,i+2)))
    {
      counter++;

    }   
    if(counter>maxCounter)
    {
      maxCounter=counter;
      counter=0;
    }            
  }  


  return maxCounter;          
}

它胜过了所有的案子，除了一个。有人能用一个for循环显示解决方案吗？

很抱歉这么晚才提到，但您不能使用正则表达式或集合框架中的任何东西。

Answer 1

我来晚了一点，但我的解决方案是：

public int maxBlock(String str) {
    int max = 0;
    int count = 1;
    char o = ' ';

    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (c == o) {
            count++;
            if (count > max) { max = count; }
        } else {
            count = 1;
            if (count > max) { max = count; }
        }
        o = c;     
    }

    return max;
}

Answer 2

您可以使用模式匹配器"（.）（\\1）*"在String中查找重复的char，代码如下：

public int maxBlock(String str) {
        Pattern pattern = Pattern.compile("(.)(\\1)*");
        Matcher matcher = pattern.matcher(str);
        int max = 0;
        while (matcher.find()) {
            max = Math.max(max, matcher.group().length());
        }
        return max;
    }

Answer 3

我认为在某些边缘情况下，您可能会弄错：

public int yourMaxBlock(String str) {
    int maxCounter = 1;
    int counter = 1;
    if (str.length() == 0) {
        return 0;
    }
    for (int i = 0; i < str.length() - 1; i++) {
        if (str.substring(i, i + 1).equals(str.substring(i + 1, i + 2))) {
            counter++;

        }
        if (counter > maxCounter) {
            maxCounter = counter;
            counter = 0;
        }
    }

    return maxCounter;
}

public int myMaxBlock(String str) {
    int maxCounter = 1;
    int counter = 1;
    if (str.isEmpty()) {
        return 0;
    }
    for (int i = 1; i < str.length(); i++) {
        if (str.charAt(i - 1) == str.charAt(i)) {
            if (++counter > maxCounter) {
                maxCounter = counter;
            }
        } else {
            counter = 1;
        }
    }

    return maxCounter;
}

public void test() {
    String[] tests = new String[]{
        "", "+", "++", "+++,++,++,+", "+,++,+++,++,", "+,++,+++,++++", "+++++,++,+++,++++"
    };
    for (String s : tests) {
        int myMax = myMaxBlock(s);
        int yourMax = yourMaxBlock(s);
        System.out.println("myMaxBlock(" + s + ") = " + myMax + (myMax != yourMax ? " WRONG! you have " + yourMax : ""));
    }
}

印刷品

myMaxBlock() = 0
myMaxBlock(+) = 1
myMaxBlock(++) = 2
myMaxBlock(+++,++,++,+) = 3
myMaxBlock(+,++,+++,++,) = 3
myMaxBlock(+,++,+++,++++) = 4 WRONG! you have 3
myMaxBlock(+++++,++,+++,++++) = 5 WRONG! you have 4