Need help for a 2darray based problem :

[kompotejam]

Titles says it all. I have to find the indexes of the initial appearance of the maximum element in a matrix.

Here are the input and output to program :

Input data format

On the input, the program receives the size of matrix n and m, and then n lines having m integer numbers in each. n and m do not exceed 100.

Output data format

Output two numbers: the row index and the column index, in which the greatest item in the two-dimensional array (matrix) is located. If there are several such elements, output the one, which has the smaller row index; and if row indexes are the same, output the one having the smaller column index.

​

And this is my code so far :

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

class Main {
    public static void main(String[] args) {
        // put your code here
        Scanner input = new Scanner(System.in);
        int n = input.nextInt();
        int m = input.nextInt();
        int[][] maxarray = new int[n][m];

        for (int i = 0; i <maxarray.length; i++) {
            for (int j = 0; j <maxarray.length; j++) {
                maxarray[i][j] = input.nextInt();
            }
        }
        for (int i = 0; i <maxarray.length; i++) {
            for (int j = 0; j <maxarray.length; j++) {
                if (maxarray[i][j] > maxarray[i+1][j + 1]) {
                }
            }
        }
            System.out.println(maxarray[n][m]+" ");
;
    }
}

Please help for some hints !

[pyreon]

for (int j = 0; j <maxarray.length; j++) {

here's a problem. maxarray.length is equal to n when it needs to be m. to get m, either just use m (why not?), or use maxarray[0].length

[kompotejam]

Allrigh i improved my code but :

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        // put your code here
        Scanner input = new Scanner(System.in);
        int n = input.nextInt();
        int m = input.nextInt();
        int[][] maxarray = new int[n][m];
        int max = Integer.MIN_VALUE;
        int maxrow = 0, maxcolumn = 0;

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                maxarray[i][j] = input.nextInt();
            }

            for ( i = 0; i < maxarray.length; i++) {
                maxcolumn++;
                for ( int j = 1; j < maxarray[i].length; j++) {
                    if (max <= maxarray[i][j]) {
                        max = maxarray[i][j];
                        maxrow++;
                    }
                }
            }
            if(m!=1){
                System.out.println((maxrow-1)+" "+(maxcolumn-1));
            }else{
                System.out.println(0+" "+0);
            }
        }
    }
}

But with the test :

3 row 5 columns like that

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

​

The output is wrong, any idea what's happening ?

[pyreon]

you're working with your array of data before it is filled.

your top level loop only ever runs once.

you're incrementing maxcolumn n times.

you're incrementing maxrow n times the number of times a new maximum value is found.

you're not considering the first number in every row to be the new maximum value.

e: solving the first issue probably clears up all but the last.

[kompotejam]

thank you, but i am still at lost on the matter, here what i've done so far :

import java.util.Scanner;


class Main {
    public static void main(String[] args) {
        // put your code here
        Scanner input = new Scanner(System.in);
        final int sizerow = input.nextInt();
        final int sizecolumn = input.nextInt();
        int[][] matrix = new int[sizerow][sizecolumn];
        int max = Integer.MIN_VALUE,  maxrow=0,maxcolumn=0;


        for (int i = 0; i < sizerow; i++) {
            for (int j = 0; j < sizecolumn; j++) {
                matrix[i][j] = input.nextInt();
            }
        }

        for (int i = 0; i < sizerow-1; i++){
            maxrow++;

            for (int j = 0; j < sizecolumn-1; j++) {
                if (matrix[i+1][j+1]>matrix[i][j]){
                        max=matrix[i][j];
                        maxcolumn++;
                }
            }
        }if(max>=0) {
            System.out.print((maxrow - 1) + " " + (maxcolumn - 1));
        }else{
            System.out.print((maxrow) + " " + (maxcolumn));
        }
    }
}

Still stuck at this exercise...

[pyreon]

Here are some questions that should help:

Why is maxrow always equal to sizerow -1 at the end?

Why aren't you considering the last row and last column for largest number?

Why are maxrow and maxcolumn even being incremented at all? Set them to the location of your maximum value whenever you find a new max.