Java: Swap 2D array rows that contain minimum and maximum values

Question

I'm having problems making a function that would swap a 2Dimensional Arrays rows, that include the biggest and the smallest values.

I cant think of a way how to make it into a code. I need a helping hand. I tried to edit the code of min and max value in an array to give me the row index of the biggest and smallest numbers but i got confused and im not sure how to do it. Pls help me on how to get the arrays row index of the max and min values so I can put it into the row switching function.

ANSWER EXAMPLE:
if the array was like this:
5   2  1  8
15 -4  5  18
7   3  44 9
12  1  18 76 
it would swap it like this:
5   2  1  8
12  1  18 76
7   3  44 9
15 -4  5  18

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        {
        
        final int kolonna = (int) (Math.random()*(9-1+1)+1);
        final int rinda = (int) (Math.random()*(9-1+1)+1);
        
        int [][] arr = new int [kolonna][rinda];
            
        //fill the grid
        for (int rin = 0; rin < arr.length; rin++) {
            
            for (int kol = 0; kol < arr[rin].length; kol++) {
                
                arr[rin][kol] = (int) (Math.random() * 201) - 100;
            }
        }
print2Dmas(arr);
System.out.println();
int mazs=0;
int liels=0;
for (int i = 0; i < arr.length; i++) {
int rowWithMin = i;
int rowWithMax = i;
    for (int j = 0; j < arr[i].length; j++) {
        if (rowWithMin > arr[i][j]) {
            rowWithMin = i;
            mazs = j;
        }

        if (rowWithMax < arr[i][j]) {
            rowWithMax = i;
            liels = j;
        }
    }
    if (rowWithMin != rowWithMax){
        swapRows(arr, rowWithMin, rowWithMax);}
}
print2Dmas(arr);
      }
    }   
    public static void print2Dmas(int mas[][]) {
        for(int i = 0; i < mas.length; i++) {

            for(int j = 0; j < mas[i].length; j++) {
                    
                System.out.print(mas[i][j] + " ");
                //System.out.println();
            }
            System.out.println();
        }
    }
    
    public static void swapRows(int array[][], int rowA, int rowB) {
           int tmpRow[] = array[rowA];
           array[rowA] = array[rowB];
           array[rowB] = tmpRow;
        }
}

Enrico · Accepted Answer · 2021-12-07 21:10:21Z

0

Store the row with the min and max value. Try this:

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        
        final int kolonna = (int) (Math.random()*(9-1+1)+1);
        final int rinda = (int) (Math.random()*(9-1+1)+1);
        
        int [][] arr = new int [kolonna][rinda];
            
        //fill the grid
        for (int rin = 0; rin < arr.length; rin++) {
            for (int kol = 0; kol < arr[rin].length; kol++) {
                arr[rin][kol] = (int) (Math.random() * 201) - 100;
            }
        }
        print2Dmas(arr);
        System.out.println();
        int rowWithMin = 0;
        int rowWithMax = 0;
        int minElement = arr[0][0];
        int maxElement = arr[0][0];
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) { 
                if (minElement > arr[i][j]) {
                    minElement = arr[i][j];
                    rowWithMin = i;
                }

                if (maxElement < arr[i][j]) {
                    maxElement = arr[i][j];
                    rowWithMax = i;
                }
            }
        }
        if (rowWithMin != rowWithMax){
            swapRows(arr, rowWithMin, rowWithMax);
        }
        print2Dmas(arr);
    }
   
    public static void print2Dmas(int mas[][]) {
        for(int i = 0; i < mas.length; i++) {
            for(int j = 0; j < mas[i].length; j++) {
                System.out.print(mas[i][j] + " ");
            }
            System.out.println();
        }
    }
    
    public static void swapRows(int array[][], int rowA, int rowB) {
           int tmpRow[] = array[rowA];
           array[rowA] = array[rowB];
           array[rowB] = tmpRow;
    }
}

Reference: Array swap - 2d array

Other example: Swapping rows of double 2d array java

edited Dec 7, 2021 at 21:10

answered Dec 7, 2021 at 17:20

Enrico

4452 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Ray8r Over a year ago

int mazs=0; int liels=0; for (int i = 0; i < arr.length; i++) { int rowWithMin = arr[i][0]; int rowWithMax = arr[i][0];     for (int j = 0; j < arr[i].length; j++) {         if (rowWithMin > arr[i][j]) {             rowWithMin = i;             mazs = j;         }          if (rowWithMax < arr[i][j]) {             rowWithMax = i;             liels = j;         }     }     if (rowWithMin != rowWithMax){         swapRows(arr,mazs,liels);} } print2Dmas(arr);

Pls help me im super dumb right now i dont know what am i doing wrong im sorry :(

Enrico Over a year ago

You are calling swapRows(arr, rowA, rowB) wrong. Use: swapRows(arr, rowWithMin, rowWithMax) So you have to pass the two rows, which have to be changed.

Ray8r Over a year ago

When i do so, it gives me a error java.lang.ArrayIndexOutOfBoundsException: Index -20 out of bounds for length 8 at Main.swapRows. Its says the error is here: int tmpRow[] = array[rowA];

Enrico Over a year ago

Oh I see you are doing: int rowWithMax = arr[i][0] Look at my code above, store the row, not the element in the row. so only int rowWithMax = i EDIT: It would be easier to understand if you could update your original post with your current code and clean it up a bit

Ray8r Over a year ago

im using int rowWithMax = i but the rows wont change, I dont understand whats wrong :(

|

Collectives™ on Stack Overflow

Java: Swap 2D array rows that contain minimum and maximum values

1 Answer 1

8 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related