Change values in array until no consecutive values

Question

I have to find an algorithm to solve this question :

You have an array with n integers in it. Make an algorithm that changes array so that there are no consecutive expressions in it and returns the amount of changes to be made.

For example in array [1,1,2,2,2] the smallest amount of changes is 2 to get it to [1,3,2,1,2].

[1,2,3,4,5] results output "0", [1,1,1,1,1] results output "2".

I have to change as less values as possible and my code does work as intended. On the other hand, I have the impression that it is not very efficient. What do you think ? Here it is :

import java.util.Arrays;
public static int untilNoConsecutive(int[] arr) {
 int rounds = 0;
 int arrSize = arr.length;
 for (int i = 0; i < arrSize - 2; i++) {
 if (arr[i] == arr[i + 1]) {
 arr[i + 1]++;
 if (arr[i + 1] == arr[i + 2])
 arr[i + 1]++;
 rounds++;
 }
 }
 if (arr[arrSize - 2] == arr[arrSize - 1]) {
 arr[arrSize - 1]++;
 rounds++;
 }
 System.out.println(Arrays.toString(arr)); // for testing purpose
 return rounds;
}
public static void main(String[] args) {
 int arr[] = { 1, 1, 2, 1, 1 };
 int arr2[] = { 1, 2, 3, 4, 5 };
 int arr3[] = { 1, 1, 1, 1, 1 };
 System.out.println(untilNoConsecutive(arr));
 System.out.println(untilNoConsecutive(arr2));
 System.out.println(untilNoConsecutive(arr3));

Thanks.

Answer 1

I'd avoid repeating the logic outside the loop. Just let the loop run until i < arrSize - 1, and add the condition i + 2 < arrSize to the inner if.

If I'm not mistaken, if the inner if condition is true, then the next loop unnecessarily checks the same values again, so I believe you could add i++ to that inner if block.

Finally some style remarks:

• You should always use braces, even on one line blocks.
• I'm not really happy with the variable names:
  • arr should probably be called array or maybe something that doesn't represent the data format such as numbers.
  • arrSize could just be called size or len(gth).
  • And rounds should (based on the task description) be changes.

• lux: Okay, so I did what you said. Thank you very much! You were right about the inner if condition, I had not much to change to get this to work. I'm used to my teacher doing those one line blocks without the braces so that's why... I also changed this! Also thanks for those remarks about variable names. I will try to do so now.