int linearSearch(int[] array, int target) {
    for 0 <= i < array.length {
    	if array[i] == target {
	   return i
	} else if array[i] > target {    // this else clause is only valid if we know that the array is already sorted
	   return -1
	}
    }

    return -1
}






int binarySearch(int[] array, int target) {
    int first = 0
    int last = array.length - 1
    int middle

    while first <= last {
    	  middle = (first + last) / 2

	  if array[middle] == target {
	     return middle
	  } else if target < array[middle] {
	    last = middle - 1
	  } else {
	    first = middle + 1
	  }
    }

    return -1
}




int recursiveBS(int[] array, int target, int first, int last) {
    if (first > last) {
       return -1
    }
    
    int middle = (first + last) / 2

    if array[middle] == target {
       return middle
    } else if target < array[middle] {
      return recursiveBS(array, target, first, middle - 1)
    } else {
      return recursiveBS(array, target, middle + 1, last)
    }
}

_____________

array
target
first 0
last  9
middle 4
_____________

array
target
first 0
last  3
middle 1
_____________

array
target
first 2
last  3
middle 2

_____________