Can someone help me with this Java Code?

[quantumlight]

Hey guys, my teacher for Computer Science AP told us to merge sort two already sorted arrays combined together.

The array given is:

{1,5,10,15,20,25,3,4,12,21,22}

Array section 1 starts at 0 and ends at 5.
Array section 2 starts at 6 and ends at 10.

basically we are to write a code that will sort the above into:

{1,3,4,5,10,12,15,20,21,22,25}

What I got so far

public int[] merge(int[] list, int a, int b, int c){
//pre: a < b and a and b are within the array bounds
//post: returns a sorted array
int[] temp = new int[ list.length ];

//YOUR CODE TO MERGE
int pos1 = a;
int pos2 = b;
int dest = 0;
for (int i = 0; i< list.length; i++) { //filling temp
temp[i] = list[i];
}
while ( (dest < temp.length) || (pos1 < b) || (pos2 < c) ){ //conditions
if (temp[pos1] < temp[pos2]) {
temp[dest] = temp[pos1];
pos1++;
dest++;
}
else {
int temporary = temp[pos2]; //hold the value at pos2

for (int i = dest; i< pos2; i++) { //shift array one over
temp[i+1] = list[i];
}
temp[dest] = temporary; //put value at pos2
pos2++;
dest++;

for (int h = 0; h < list.length; h++) { //refill list
list[h] = temp[h];
}


}
}
return(temp);
}

The output I'm getting is basically 1 followed by all 3's. I know that somehow the 3 is getting shifted over too. However when I change where the array gets shifted, it still gives me the same printout.

[taz480]

Please don't ask people here to do your homework for you.

[sr71000]

taz there's nothing wrong with asking for help. We can't all understand everything all the time. I'll be back later to see if i can help. in class and i just got a text, so now i have to behave...whoops

/edit. Looking at your code, you're not implementing merge sort correctly. Merge sort should be a recursive algorithm unless he just wants you to code one pass

http://en.wikipedia.org/wiki/Merge_sort

you have no comments saying what should be in a, b, and c...fix that!

/edit2. Also, you should wrap your code in the code tags. if you go to the advanced post options, you should see a button with the label "#" Click that and put your code inside of those tags...it helps it stand out.

alternatively you can do

{code} this is my code {/code} - you just have to change the {} to []

it'll look like this

 this is my code

. This will preserve your formatting (such as indents) and make your code stand out from the rest of your post! Makes it much easier to handle!

I'm going to repost your code properly formatted and such inside the code tags.

[sr71000]

/* merge(int[] list of ints to be sorted, int ?, int ?, int ?)
  *
  * PRE/POST CONDITIONS
  * pre: a < b  and a and b are within the array bounds
  * post: returns a sorted array
  */
public int[] merge(int[] list, int a, int b, int c)
{
	//Declare Variables
	int[] temp = new int[ list.length ];
	int pos1 = a;
	int pos2 = b;
	int dest = 0;

	//filling temp - why?  Why not just pull values straight from list as you go?
	for (int i = 0; i< list.length; i++)
		temp[i] = list[i];

	while ( (dest < temp.length) || (pos1 < b) || (pos2 < c) )
	{
		if (temp[pos1] < temp[pos2])
		 {                                           
			temp[dest] = temp[pos1];
			pos1++;
			dest++;
		}
		else 
		{
			//hold the value at pos2
			int temporary = temp[pos2];   
                      
			//shift array one over
			/////////////////////////////////////////
			//HERE IS YOUR MAJOR ISSUE!!!!!
			/////////////////////////////////////////
			//Remember when you do this, you're shifting the remainder of your array to the right 1 space.  That means you're moving position 1 and two as well as the beginning and the end of both parts of your array! (meaning a, b, and c)
			//Since you may also be changing a, b, and c we need to know exactly what they are!  WE NEED MORE INFO ABOUT A, B, AND C!!!  I'm only being a pita about this because this may be a simple problem but if you're going to ask for help you need to learn to properly document, especially with your input variables!
			/////////////////////////////////////////
			for (int i = dest; i< pos2; i++)
				temp[i+1] = list[i];
			temp[dest] = temporary;                               //put value at pos2
			pos2++;
			dest++;
			for (int h = 0; h < list.length; h++)                //refill list
				list[h] = temp[h];
		}
	}
	return(temp);
}

I know what a, b, and c do, but i'm not helping any more till I see proper documentation except to say you should rethink your design entirely. You're doing SO much more work than you have to. Rethink this without filling temp first and then trying to sort them in place (in the array). There's a much easier way to do this!

-Kevin

[jd123]

void merge_sort(apvector <int> &arrayA, apvector <int> &arrayB, apvector <int> &arrayC)
{
int indexA = 0; // initialize the Array Indices
int indexB = 0;
int indexC = 0;

while((indexA < arrayA.length( )) && (indexB < arrayB.length( ))
{
if (arrayA[indexA] < arrayB[indexB])
{
arrayC[indexC] = arrayA[indexA];
indexA++; //increase the index
}
else
{
arrayC[indexC] = arrayB[indexB];
indexB++; //increase the index
}
indexC++; //move to the next position in the new array
}
// Push remaining elements to end of new array when 1 feeder array is empty
while (indexA < arrayA.length( ))
{
arrayC[indexC] = arrayA[indexA];
indexA++;
indexC++;
}
while (indexB < arrayB.length( ))
{
arrayC[indexC] = arrayB[indexB];
indexB++;
indexC++;
}
return;
}

/************************************************** ************/
*this checks which item is smaller and puts it in array C while there are still items,
* when one stack runs out it adds the rest of the items to the end of Arrray C.
* enjoy
***************************************/