#include <stdio.h>
#include <stdlib.h>

int numOfCalls = 0;
int binarySearch(int* sequence, int element, int firstIndex, int lastIndex) {
  //return the index of element in sequence.

  numOfCalls++;

  int middleIndex = firstIndex + (lastIndex - firstIndex ) / 2;
  if (sequence[middleIndex] > element) {
    //The element is before middleIndex.
    return binarySearch(sequence, element, firstIndex, middleIndex -1);
  } else if (sequence[middleIndex] == element) {
    //Found the element.
    return middleIndex;
  } else if (sequence[middleIndex < element]) {
    //The element is after middleIndex.
    return binarySearch(sequence, element, middleIndex + 1, lastIndex);
  }

}

main(int argn, char** args) {
  /* The first parameter is the number of elements in the sequence.
     The elements will be 0, 1, 2, ... args[1]-1.
     The second parameter is the searched element. */

  int numOfElements = atoi(args[1]);
  int* sequence = (int *)malloc(sizeof(int)*numOfElements);

  for (int i=0; i<numOfElements; i++) {
    sequence[i] = i;
  }

  printf("Det sökta elementet finns på index %d.\n", 
	 binarySearch(sequence, atoi(args[2]), 0, numOfElements));
  printf("Det krävdes %d rekursiva anrop.\n", numOfCalls);

}