Hello gentlemen!
can any of you guys help me understand why this script is returning 100 instead of the median?
[CODE]
package eksamen;
public class Kap7opg7 {
public static void main (String[] args){
//int []b = new int[1000];
//int x;
//for (x = 0; x < b.length; x++){
// b[x] = x;
//}
int []b = {1,4,6,8,12,15,18,22,26,34,53,62,77,89,92,94,100};
System.out.println(median(b));
}
static int median (int[] a){
int ca = 0;
int med1 = (a[a.length/2]);
int med2 = (a[(a.length/2)+1]);
int medsum = ((med1 + med2) / 2);
int j;
do{
for (j = 0; j < a.length; j++){
if (a[j] >= medsum){
ca = a[j];
}
}
}while (ca < medsum);
return ca;
}
}
[/CODE]
As you're assuming that the array is sorted you should grab the median without a loop.
Other than that, you have two loops, the inner of which always runs for all elements and will overwrite [I]ca[/I] with all elements larger than medsum, the last of which is 100.
The correct solution would be to check whether the length of a is even, then if it is to grab the values at a.length/2 and a.length/2-1 and return the average.
If it isn't the value at a.length/2 (truncated) should be the correct one.
(Assuming JS has 0-based arrays.)
Maybe there's a way to avoid branching by taking advantage of integer division, but I don't know that off the top of my head right now.
Maths references usually assume an index of 1 for the first element, so you have to take an offset of 1 into account when accessing the array.
First of all, indent your code, if you don't you are just making it harder for yourself.
The first 4 lines of the function pretty much got you there.
I have literally no clue what you where trying to do in the last 10 lines.
[cpp]static int median(int[] a)
{
if(a.length % 2 == 0) // Is the length even?
return (a[(a.length - 1)/2] + a[(a.length - 1) / 2 -1]) / 2 // Return the mean
else
return a[a.length - 1)/2 ] // Return the median
}
[/cpp]
Edit: RTFM
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