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April 7, 2015 22:03
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Khan Academy Binary Search Challenge
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/* 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 i = 1; | |
while (max >= min){ | |
guess = Math.floor((max + min)/2); | |
if(array[guess] === targetValue){ | |
println("Total guesses " +i); | |
return guess; | |
} | |
else if (array[guess] < targetValue){ | |
min = guess +1; | |
} | |
else { | |
max = guess -1; | |
} | |
i = i+1; | |
println(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, 5); | |
//println("Found prime at index " + result); | |
Program.assertEqual(doSearch(primes, 73), 20); | |
Program.assertEqual(doSearch(primes, 97), 24); | |
Program.assertEqual(doSearch(primes, 11), 4); |
Cleared up the portion about the guess.
/* 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 guesses = 1;
while(min<= max){
guess = Math.floor((min + max)/2);
if(array[guess] === targetValue){
println(guess);
println(guesses);
return guess;
}
else if(array[guess] < targetValue){
min = guess + 1;
}
else{
max = guess -1;
}
guesses = guesses + 1;
}
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, 73), 20);
Program.assertEqual(doSearch(primes, 97), 24);
Program.assertEqual(doSearch(primes, 11), 4);
What do the arguments 20, 24 and 4 signify?
The second argument of Program.assertEqual refers to the number of the index in test example, index 18 has the prime number 67 and index 12 has the prime number 41.
- Program.assertEqual(doSearch(primes, 67), 18);//test
- Program.assertEqual(doSearch(primes, 41), 12);//test
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 doSearch = function(array, targetValue) {
var min = 0;
var max = array.length - 1;
var guess;
var intentos = 0;
while(max >= min){ //stop loop if targetValue is not array
intentos++;
guess = Math.floor((min + max)/2);
println(guess);
if(targetValue === array[guess]){
println("intentos realizados: " + intentos);
return guess;
}
else if(array[guess] < targetValue){
min = guess + 1;
}
else{
max = guess - 1;
}
}
return -1;
};
var result = doSearch(primes, 41);
println("Found prime at index " + result);
Program.assertEqual(doSearch(primes, 73), 20);
Program.assertEqual(doSearch(primes, 67), 18);//test
Program.assertEqual(doSearch(primes, 41), 12);//test
Program.assertEqual(doSearch(primes, 73), 20);
Program.assertEqual(doSearch(primes, 97), 24);
Program.assertEqual(doSearch(primes, 11), 4);What do the arguments 20, 24 and 4 signify?
the index of targetValue
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are you setting var i to 1; in order to account for the initial number, but how does this count as a guess.