CODEWITHSUNDEEP
javaarrays
Deepak
Deepak

Reputation: 2102

Please help me solve my Java homework about arrays

Problem Statement:

Given an array of ints, compute if the array contains somewhere a value followed in the array by that value times 10. We'll use the convention of considering only the part of the array that begins at the given index.The initial call will pass in index as 0.

Examples:

public boolean array220(int[] nums, int index)

array220({1, 2, 20}, 0) → true
array220({3, 30}, 0) → true
array220({3}, 0) → false**

I'm stuck with the problem with no approach to solve it.

Upvotes: 0

Views: 1037

Answers (4)

Carl Manaster
Carl Manaster

Reputation: 40336

for (int i = index; i < nums.length - 1; i++) 
    if (nums[i] * 10 == nums[i + 1]) return true;
return false;

Upvotes: 2

Shaded
Shaded

Reputation: 17826

Recursive answer just for the hell of it... also I wouldn't post this is there weren't already valid answers. Make an attempt and post what you tried.

public boolean array220(int[] nums, int index){
    if(index >= nums.length - 1)
        return false;
    if(nums[index] * 10 == nums[index + 1]){
        return true;
    } else {
        return array220(nums, ++index);
    }
}

Upvotes: -1

Adam Batkin
Adam Batkin

Reputation: 52984

I'm not going to give you the answer as a Java program, since a number of folks have already done that.

When in doubt, try writing out the program in English (or any other native tongue). If you can't write it out in complete detail, write out what you can, and then refine in pieces.

Given an array of ints, compute if the array contains somewhere a value followed in the array by that value times 10. We'll use the convention of considering only the part of the array that begins at the given index.The initial call will pass in index as 0.

What do we know here? We have an array and a starting index. So, what do you want to do? Maybe that's a bit complicated, so if we were doing it by hand, how would you start?

  1. Look at the first element of the array (where "first" is the starting index)
  2. Look at the next element of the array and divide it by 10
  3. Look at the results from steps #1 and #2. Are they the same?
    • If they are, return true
    • If they are not, start back again at step #1, but look at the following elements instead

Then refine that further:

  1. Set the current index to be the starting index
  2. For each element of the array, from the current index through the end:
    1. Get the following element and divide by 10
    2. Are the two numbers equal? If so, we're done, return true
    3. If not, increment the current index and repeat

You may notice that there is a small issue with step #2: You don't want to loop all the way to the end. Because if you do that, there won't be any "next" element to compare it to. So really you want to loop to the second-to-last element.

Continue refining. At some point you can translate directly to Java or whatever programming language you want. (If you can't do this last step, you need to add an additional step 0: Learn the programming language first)

Upvotes: 1

Matthew Cox
Matthew Cox

Reputation: 13672

I'll give you some psuedo code to work with.

Let `nums` be my array

Let `i` be the starting index

Let `index` be `i + 1`

for all indices < array's length, iterate

   Let currNum be `array[index - 1]`

   if currNum times 10 equals `array[index]`
      return true

   increment index

return false because we found no numbers that we true

Upvotes: 2

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