Iterating over a string array

Question

Return true if the string "cat" and "dog" appear the same number of times in the given string.

catDog("catdog") → true

catDog("catcat") → false

catDog("1cat1cadodog") → true

public boolean catDog(String str) {
  int countCat=0;
  int countDog=0;

  for(int i=0;i<str.length()-3;i++){
    if(str.substring(i).startsWith("cat")){
      countCat++;
    }
    if(str.substring(i).startsWith("dog")){
      countDog++;
    }
  }
  if(countCat==countDog){
    return true;
  }
  else{
    return false;
  }
}

I am having trouble writing this method. Does anybody know why my code doesn't work correctly? Edit: The code compiles, however it gives the wrong output. For example if i put in "catdog" it returns false.

Have you checked, that you iterate the correct amount of times? Because you currently don't. — Tom, Dec 16 '16 at 12:34
I got it, I got it. I was working with substring(i,i+3) and forgot to change the length of iteration steps when I started using startsWith. — DerDieDasEhochWas, Dec 16 '16 at 13:06

XtremeBaumer · Answer 1 · 2016-12-16T12:42:32.407

with the examples you posted, its because of your for loop which should be for(int i=0;i<str.length();i++){. you can also use str.length()-1 and str.length()-2 to get the right result. -3 will give the wrong result. little example: string is catdog1dog. result should be false. lets have a look at the substring which will be created with -3:

catdog1dog
atdog1dog
tdog1dog
dog1dog
og1dog
g1dog
1dog

as you can see with -3 the last substring is wrong and therefore the result too. that is because if you look at substring, you will see that the start is at char 0 and not at 1 therefore str.length()-1 is the last character in your string. sorry if my explanations isn't that good

Thanks, i was working with substring(i,i+3) before and forgot to change it. — DerDieDasEhochWas, Dec 16 '16 at 13:05

score 0 · Answer 2 · edited May 23 '17 at 11:45

0

As suggestsed in this question, I would recomment using StringUtils.countMatches from Apache Commons Lang?

Credit to @A_M

edited May 23 '17 at 11:45

Community

1
1

answered Dec 16 '16 at 12:40

alexdriedger

2,884
2
23
30

score 0 · Answer 3 · answered Dec 16 '16 at 12:45

0

Although your problem can be solved through other strategies, I think you might only subtract 2 to str.length() instead of 3.

I hope be useful!

answered Dec 16 '16 at 12:45

Rachel M. Carmena

91
3

score 0 · Answer 4 · answered Dec 16 '16 at 12:45

I would do something like this:

public boolean catDog(String str){
    return countWords(str, "cat") == countWords(str, "dog");
}


private int countWords(String original, String word){
    int counter = 0;
    boolean searching = true;
    while(searching){
        if(original.indexOf(word) >= 0){
            counter++;
            original = original.substring(original.indexOf(word) + word.length());
        }
        else{
            searching = false;
        }
    }
    return counter;
}

Iterating over a string array

4 Answers4