Finding the biggest number in java two-dimentional array

Question

I am getting output as 91. If I alter for(int j=0;j<=arr.length;j++) then I am getting output as 92. But the actual answer is 93.

package basics;

public class maximumNumber {
    public static void main(String[] args) {
        int arr[][] = {‌{11,21,31,32,33},{41,51,61,62,63},{71,81,91,92,93}};
        int max = arr[0][0];

        for(int i=0;i<arr.length;i++) {
            for(int j=0;j<arr.length;j++) {
                if(arr[i][j]>max) {
                    max=arr[i][j];
                }
            }
        }

        System.out.println(max);
    }
}

Go into your IDE, enable debugmode and go through the program step by sted and see how the values change. Then you will see why — fedoraHacker, Apr 07 '20 at 18:46
Does this answer your question? [Java: Finding the highest value in an array](https://stackoverflow.com/questions/1806816/java-finding-the-highest-value-in-an-array) — fuggerjaki61, Apr 07 '20 at 18:50
@fuggerjaki61 It's a different problem - the problem in this case is the loop condition. — EJoshuaS - Stand with Ukraine, Apr 07 '20 at 18:52
Weird question: can you [accept whichever answer you found most helpful](https://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work)? (It helps future readers with similar problems identify the answer that worked best for you). — EJoshuaS - Stand with Ukraine, Apr 08 '20 at 14:03

EJoshuaS - Stand with Ukraine · Answer 1 · 2020-04-07T22:07:34.437

The problem is here:

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

You should actually be looping over the length of the inner array, not of the outer array. This should actually be

for(int j=0;j<arr[i].length;j++)

Edit: A key piece of information here is that you have an array of arrays. Your "outer" array has 3 items, each of which is itself an array of integers. To help understand this, try running the following code:

public class maximumNumber {
    public static void main(String[] args) {
        int arr[][] = {{11,21,31,32,33},{41,51,61,62,63},{71,81,91,92,93}};
        int max = arr[0][0];

        for(int i=0;i<arr.length;i++) {
            int[] innerArray = arr[i];

            System.out.println("------------------ Begin array " + i + " -----------");

            for(int j=0; j< innerArray.length; j++) {
                System.out.println(innerArray[j]);

                if(arr[i][j]>max) {
                    max=arr[i][j];
                }
            }

            System.out.println("------- End of array " + i + " --------");
        }

        System.out.println(max);
    }
}

Here's the output:

------------------ Begin array 0 -----------
11
21
31
32
33
------- End of array 0--------
------------------ Begin array 1 -----------
41
51
61
62
63
------- End of array 1--------
------------------ Begin array 2 -----------
71
81
91
92
93
------- End of array 2 --------
93

To understand deeply arr.length=3. I can understand it is returning number of rows value. what is arr[i].length. I tried to print this arr[i].length it is printed as 5. Could you please help me how it returned as 5 — Balaji Santhanam, Apr 07 '20 at 21:24

score 5 · Answer 2 · edited Apr 07 '20 at 20:50

5

In second loop u need to use arr[i].length

  int arr[][] = {{11,21,31,32,33},{41,51,61,62,63},{71,81,91,92,93}};

  int max = arr[0][0];

   for(int i=0;i<arr.length;i++){
          for(int j=0;j<arr[i].length;j++){
                if(arr[i][j]>=max){max=arr[i][j];}
           }
     }

edited Apr 07 '20 at 20:50

Dumidu Udayanga

864
2
9
21

answered Apr 07 '20 at 18:46

mr. pc_coder

16,412
3
32
54

Looks like the three of us came up with the answer more or less simultaneously :) – EJoshuaS - Stand with Ukraine Apr 07 '20 at 18:50

score 5 · Answer 3 · answered Apr 07 '20 at 18:46

5

Your condition j<arr.length is wrong. arr.length is 3, but you need j to continue until 5, the length of your subarrays.

Should be j < arr[i].length.

answered Apr 07 '20 at 18:46

khelwood

55,782
14
81
108

Looks like the three of us came up with the answer more or less simultaneously :) – EJoshuaS - Stand with Ukraine Apr 07 '20 at 18:50

score 1 · Answer 4 · answered Apr 07 '20 at 19:15

1

In the second loop use for (int j = 0; j < arr[i].length; j++) {, this will give you full element loop.

answered Apr 07 '20 at 19:15

Duricic Milos

34
2

@ParthSane sure: this way we are taking into account all the values of each subarray – Duricic Milos Apr 09 '20 at 22:41
@EJoshuaS-ReinstateMonica you are right. Now see the first answer is very descriptive. I think I have tried vote up but only thing I can do with current rank is give answers and comment – Duricic Milos Apr 09 '20 at 22:45

Mr. Polywhirl · Answer 5 · 2020-04-07T19:10:26.420

Starting with Java 8, you can use streams to do this.

e.g. intStream.max(Integer::compare)

But you will need to flatten the data first.

import java.util.Arrays;
import java.util.stream.Stream;

public class Flatten {
    public static void main(String[] args) {
        int arr[][] = {
            { 11, 21, 31, 32, 33 },
            { 41, 51, 61, 62, 63 },
            { 71, 81, 91, 92, 93 }
        };
        System.out.printf("Max: %d", max(arr));
    }

    private static int max(int[][] matrix) {
        return flatten(matrix).max(Integer::compare).get().intValue();
    }

    private static Stream<Integer> flatten(int[][] matrix) {
        return Arrays.asList(matrix).stream()
            .map(row ->  Arrays.stream(row)).flatMap(a -> a.boxed());
    }
}

Even if this is technically correct, the OP might to be new to Java, so they may find it confusing (especially since there's not a lot of commentary on how it works) — EJoshuaS - Stand with Ukraine, Apr 07 '20 at 22:09

Finding the biggest number in java two-dimentional array

5 Answers5