Question

Suppose we have an array of integers. We’ve written a function to fetch the index of the first specified value in the array, or -1 if the array does not contain the value..

So for example, if the array = { 4, 5, 4, 4, 7 }, then getFirstIndexOf(4) would return 0, getFirstIndexOf(7) would return 4, and getFirstIndexOf(8) would return -1.

Below, I have presented three different ways to write this function. It is a widely accepted coding standard that returns in the middle of functions, and breaks in the middle of loops are poor practice. It seems to me that this might be an acceptable use for them.

public int getFirstIndexOf(int specifiedNumber) {
  for (int i = 0; i < array.length; i++) {
    if (array[i] == specifiedNumber) {
      return i;
    }
  }

  return -1;
}

VS.

public int getFirstIndexOf(int specifiedNumber) {
  int result = -1;
  for (int i = 0; i < array.length; i++) {
    if (array[i] == specifiedNumber) {
      result = i;
      break;
    }
  }

  return result;
}

VS.

public int getFirstIndexOf(int specifiedNumber) {
  int result = -1;
  for (int i = 0; i < array.length; i++) {
    if (array[i] == specifiedNumber && result == -1) {
      result = i;
    }
  }

  return result;
}

What do you think? Which is best? Why? Is there perhaps another way to do this?

Answer 1

That’s why do…while & while loop was invented.

As requested:

public int getFirstIndexOf(int specifiedNumber) {
    int i = array.Length;
    while(--i > -1 && array[i] != specifiedNumber);

    return i;       
}