Binary Search

Programming Language:

Javascript (JS)

Solution:

/* Returns either the index of the location in the array,
  or -1 if the array did not contain the targetValue */
var doSearch = function(array, targetValue) {
	var min = 0;
	var max = array.length - 1;
    var guess;
    var countguess = 0;

    while(min <= max)
        {
            guess = Math.floor((max+min)/2);
            countguess++;
            println(guess);
            if(array[guess] < targetValue)
            {min = guess+1;}
            else if (array[guess] > targetValue)
            {max = guess-1;}
            else
            {println(countguess);return guess;}
        }
    return -1;
};

var primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 
		41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97];

var result = doSearch(primes, 73);
println("Found prime at index " + result);

Program.assertEqual(doSearch(primes, 73), 20);
Program.assertEqual(doSearch(primes, 71), 19);
Program.assertEqual(doSearch(primes, 2), 0);