Java- Finding maximum number in a 2D array

Question

This program compares two numbers in a 2*5 array which the user inputs and displays the largest number between the two. But I have some problem in understanding what [0] really does in int max = array[i][0]. I mean, shouldn't it be int max = array[i][j]? Because basically, what I understand from array[i][0] is that the numbers being input for the rows is being compared with the first element of the column since it's [0] but I would like some explanation how it actually works.

import java.util.*;

public class L2 {

    public static void main(String[] args) {

        Scanner input= new Scanner(System.in);

        System.out.println("Please enter 10 integers");

        int array[][]= new int[2][5];

        for(int i=0; i<array.length; i++){

            int max= array[i][0];
            for(int j=0; j<array[i].length; j++){

                array[i][j]= input.nextInt();

                if(max<array[i][j]){

                    max= array[i][j];
                }
            }
            System.out.println("Maximum number in the row is "+ max);
            System.out.println();
        }              

    }

}

hugh · Accepted Answer · 2015-08-16 12:44:45Z

2

It's taking a 2*5 array of integers and finding the maximum in each row of 5, (then presumably summing these (2) values up, although that code isn't included in your snipper).

The line

int max= array[i][0];

is initializing the maximum value on the ith row to the first value in that row, than scanning the row to find any larger and increase max accordingly. Typically you'd then start the loop counter from 1, since the 0th value is already dealt with:

for(int j=1; j<array[i].length; j++){

Another common approach is to initialize max to MIN_INT instead, since all values will be greater than this.

answered Aug 16, 2015 at 12:44

hugh

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2 Comments

Tia Over a year ago

No, it would loop through the columns only 4 times if I start the loop counter for the inner loop from 1. It should start as from 0 only.

hugh Over a year ago

It would, but this would give the correct answer - max starts from the value of the first element, then this is compared with each of the remaining (4) values. It's not necessary to compare this value with the zeroth element, since it was already set equal to it, so you save one loop iteration. (Of course, the extra iteration won't change the result, so if you find this way more readable you might prefer to leave it in.)

CodeExplorer · Accepted Answer · 2023-02-13 14:48:54Z

//I hope this helps you 
    public class Compare{


        public static void main(String[] args) {

            Scanner input= new Scanner(System.in);
            int row = 2;
            int col = 5;
            int array[][]= new int[row][col];
            System.out.println("Please enter 10 integers");
            for(int i=0; i<row; i++){
                for(int j=0; j<col;j++){
                    array[i][j]= input.nextInt();
                }
            }

            System.out.println(Arrays.deepToString(array));
            int max = Integer.MIN_VALUE;
            for(int i=0; i<row; i++){
                for(int j =0; j<col; j++){
                    if(max<array[i][j]){
                        max = array[i][j];
                    }
                }
                System.out.println("Maximum number in the row is "+ max);
            }

        }

    }

Amit Bhati · Accepted Answer · 2015-08-16 12:44:47Z

1

In below line, the max is getting initialized with the first element of the row:-

int max= array[i][0];

Your purpose is to find the maximum of each row, so basically you are starting the every iteration with the first element of the row.

answered Aug 16, 2015 at 12:44

Amit Bhati

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Comments

Ritam Chakraborty · Accepted Answer · 2019-07-21 11:00:02Z

0

In other way you can use Collection.max(Stream.of(..).collect(Collectors.toList()));

Here's an example

System.out.println(Collections.max(Stream.of(new int[][]{{1, 2}, {3, 4}})
        .map(a -> Collections.max(Arrays.stream(a).boxed()
            .collect(Collectors.toList())))
            .collect(Collectors.toList())));
Output: 4

answered Jul 21, 2019 at 11:00

Ritam Chakraborty

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Comments

CodeExplorer · Accepted Answer · 2023-02-11 20:20:37Z

The following code allows you to enter number of columns and rows and numbers. It outputs the array of numbers and highest numbers in each column. It expands your code a bit

public static void main(String[] args) {
    System.out.print("Enter number of rows: ");
    Scanner sc1 = new Scanner(System.in);
    int row = sc1.nextInt();
    
    System.out.print("Enter number of columns: ");
    Scanner sc2 = new Scanner(System.in);
    int col = sc2.nextInt();


    System.out.print("Enter numbers: ");
    Scanner sc = new Scanner(System.in);


    int array[][] = new int[row][col];

    for(int i = 0; i < row; i++) {
        for(int j = 0; j < col; j++) {
            array[i][j] = sc.nextInt();
        }
    }

    System.out.println(Arrays.deepToString(array));

    int max = Integer.MIN_VALUE;
    int[] arrayMax;
    System.out.print("Maximum numbers are: ");
    for(int i = 0; i < row; i++){
        for(int j = 0; j < col; j++) {
            if(max < array[i][j]) max = array[i][j];
        }
        arrayMax = new int[]{max};
        System.out.print(Arrays.toString(arrayMax) + ", ");

    }

}

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