Using the two functions that respectively return the first and the last indices of an item in an array (and -1 if the item doesn't exist in the array), define a function that returns true if the passed item occurs exactly once in the array, false otherwise.

int indexOf(int[] data, int item) {
  for(int i=0; i < data.length; i++) {
    if(data[i] == item) {
       return i;
    }
  }
  return -1;
}

int lastIndexOf(int[] data, int item) {
  for(int i=data.length-1; i >= 0; i--) {
    if(data[i] == item) {
       return i;
    }
  }
  return -1;
}