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This is my homework which is due tomorrow and I have been trying to do it for the past 5 hours, but I can't figure it out. I understand what I have to do, but I just don't know where to start. If you could help me to just get started or to give some advice it would be great. Can i just have the answer I cant figure it out iv tried everything

It has to Return an array of int, of size 27, consisting of character counts from the String s.

  • The count of the number of 'a' or 'A' characters must be in position 0 of the array,
  • the count of the number of 'b' or 'B' characters must be in position 1 of the array,
  • the count of the number of 'z' or 'Z' characters must be in position 25 of the array, and
  • the count of all other characters must be in position 26 of the array.

for example

  • if s is "", then all entries in the array must be 0.
  • if s is "a", then all entries in the array must be 0 except for entry 0, which must be 1.
  • if s is "Baaa!", then all entries in the array must be 0 except for:
    • entry 0, which must be 3,
    • entry 1, which must be 1, and
    • entry 26, which must be 1.

The only methods you may call on the String s are charAt(int) and length().

Thanks iv read everything you guys have said and its helped me alot in understanding the problem and what i need to do. Im still stuck however but im slowly getting this. Thanks again!

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    well, you can show us some code to see where you're stuck at. Commented Feb 10, 2011 at 20:31

4 Answers 4

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  1. Create an array of 27 elements. Official trail on Arrays

  2. Iterate through all characters of the string, using for instance an ordinary for loop (Official trail on the for statement) and the String.charAt.

  3. Find the index corresponding to the character using something like Character.toUpperCase(currentChar) - 'A' for ordinary characters.

  4. Increment the corresponding entry in the array, using something like charSums[index]++.

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+1. Also worth noting: you can convert back and forth between the letter of the alphabet and the index in the array.
It seems he is not allowed to use String.toCharArray, but String.charAt is good enough anyway.
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So, basically you are trying to count the numbers of occurrence of alphabets in a String.

The returning array is size 27 because there are 26 alphabets + 1 cell of non-alphabet characters.

What you need to do is simple, 1) create array of size 27 (no need for special initialization since java initialize int array to 0s for you),

2) iterate through the string using lenght() method

3)at each iteration use the chartAt() method to get the character and increment the count in the correct cell of array you created in step 1.

Hint: consider what will 'b'-'a' and 'z'-'a' return.

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I was going to add the bit that Alvin mentioned. Rememeber that char is not just a character in a string but also a number.

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The same steps as everyone, but I may go into a lot more detail than you want on my solution at step 4, so don't read it if you don't want too much of a hint.

  1. Initialize the array (int[] array = new int[27];

  2. Convert the string toUpperCase().

  3. Create a loop to go through every character of the string.

  4. Convert the character to an array index. For this, I would suggest having an if/else converting the char you're working with to an int based off of ASCII values for capital letters (I believe you can do this by just doing an (int) or (Integer) type cast, but I don't have a compiler on this computer to check). If it falls within the range of the ASCII values for capital letters, then subtract the value for 'A', to make it 0, and use the int value to increment the value in your array. If the value isn't within the ASCII range, default to the else statement and increment a[26].

  5. Return the array after the for loop.

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