sort + search multidimensional array

[rix]

hey all

I cant seem to find any syntax to allow searching or sorting in multidimensional arrays. I have a [4][5] array that i need to sort and then binary search to return an index position for any one element. On the sun website the binary search reference shows a single int[] as an argument but there is no mention of multidimensions.

thanks

[ArchAngel]

That's because it doesn't really make sense in multi-dimension space! What are you actually trying to solve?

Consider:

{
  {2, 5, 8, 9}
  {5, 8, 2, 2, 2}
  {9, 2, 5}
}

...after sorting each dimension:

{
  {2, 5, 8, 9}
  {2, 2, 2, 5, 8}
  {2, 5, 9}
}

Now what? Let's say you wanted to find 5. It could appear in several indices:

{
  {2, 5, 8, 9}
  {2, 2, 2, 5, 8}
  {2, 5, 9}
}

...so you could do a binary search on each index and store each of the two indices ([0][1], [1][3] and [2][1]). What about duplicate data items?

[rix]

I jjust want to sort the array, index by index, i presume with a similar manner i can search the array. Do you know the syntax required to sort the array ?

[ArchAngel]

You're missing the point - WHICH array? As you can see from my example above you have an array which contains three arrays.

[rix]

ha ha, sorry im not being very specific. I was wanting to search the first row, the second row etc im trying to make loops to do this but i cant figure out the syntax.

[ArchAngel]

You're still not being very specific!

Is it that you want to find the smallest value in an array of arrays?

[rix]

import java.util.*;
class TwoDArray {
public static void main (String args[]) {

int foundAtIndex = 0;
 boolean test = false;
 int twoD[][]=new int [4][5];
 int i, j, k =0;
 for (i=0;i<4;i++) {
	for (j=0;j<5;j++) {
	k = (int)(Math.random()*5+1);
	twoD[i][j]=k;
			}
			}  

//Arrays.Sort(twoD);   

for (i=0;i<4;i++) {
for (j=0;j<5;j++) {
	System.out.print (twoD[i][j]);
		 }
	System.out.println();
		}

KeyboardInput in = new KeyboardInput(); 

System.out.println("\nPlease enter integer you wish to find:");
int intToFind=in.readInteger();
for (i=0;i<4;i++) {
for (j=0;j<5;j++) {
//int x = Arrays.binarySearch(twoD,intToFind);
if (intToFind==twoD[i][j])
	{
test=true;
	}
}
}

if (test == true)
{
System.out.print("Your integer was found ");
}
else
System.out.print("Integer not found");

}
}

Obviously for now it will only return the first instance of element it searches for, i'll deal with multiple instances later. Ideally i'll like to know how:

-to sort each row
-to search each row with binarySearch so i can be given the index value the element was found at.

hope that helps, thanks

[ArchAngel]

It's all in the java.util.Arrays class. This code will sort your multi-dimension array. From this you should be able to work out the binary search code.

import java.util.Arrays;

public class Test {
	public static void main(String[] args) {
		int[][] myArray = { {2, 5, 8, 9}, {5, 8, 2, 2, 2}, {9, 2, 5} };
		display(myArray);
		sortAll(myArray);
		display(myArray);
	}
		
	public static void display(int[][] myArray) {
		// Move through the first dimension...
		for (int i = 0; i < myArray.length; i++) {

			// Move through the second dimension...
			for (int j = 0; j < myArray[i].length; j++) {

				// Display the element.
				System.out.print(myArray[i][j] + "\t");

			}

			System.out.println();
		}
		System.out.println();
	}

		
	public static void sortAll(int[][] myArray) {
		// Move through the first dimension...
		for (int i = 0; i < myArray.length; i++) {

			// Sort the next dimension.
			Arrays.sort(myArray[i]);	

		}
	}
}

[rix]

thanks again

[ArchAngel]

No probs.