Program which counts minimum of a two dimensional int array

Question

I am trying to create a program, which counts the minimum of each dimension in a two dimensional array. So for ex. if i had an array:

int[][] test = {{1,2,3},{2,3,4},{4,5,6}}

the program would display: [1,2,4] - the minimum of each dimension. For that I've created a method called minimum, which looks like this

static int[] minimum(int[][] arr) {
        int[] result = new int [arr.length];
        for (int i = 0; i < arr.length; i++) {
            for(int j = 0; j < arr[i].length; j++) {
                int  min = arr[i][0];
                if(arr[i][j] < min) {
                    min = arr [i][j];
                    result [i] = min;
                } else{

                }
            }
        }
        return result;
    }

But when i call out this method in my main, with a sample array

public static void main(String[] args) {
            int[][] arr = {{1,2,3,},{3,4,5},{6,6,6}};
        System.out.println(Arrays.toString(minimum(arr)));


    }

The program displays [0,0,0,]. Do You have any clue where is the problem and how to fix it?

Well, int min = arr[i][0]; needs to move up one line, to outside the inner loop. But I can't see why you're getting [0,0,0]. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Jul 24, 2018 at 22:49
return Arrays.stream(arr).mapToInt(a -> Arrays.stream(a).min().getAsInt()).toArray(); — shmosel
– shmosel, Commented Jul 25, 2018 at 0:28
@DawoodibnKareem Result is [0,0,0] because if(arr[i][j] < min) is never true given that min = arr[i][0] and first element of each sub-array is the smallest, so nothing is ever assigned to result array. — Andreas
– Andreas, Commented Jul 25, 2018 at 0:32

ggorlen · Accepted Answer · 2018-07-25 00:21:47Z

3

The problem is that if the first element in the array is min, it never gets recorded to the result array. Try:

static int[] minimum(int[][] arr) {
    int[] result = new int[arr.length];

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

        for (int j = 1; j < arr[i].length; j++) {
            if (arr[i][j] < result[i]) {
                result[i] = arr[i][j];
            }
        }
    }

    return result;
}

Note that there needs to be at least one element per row in the input matrix for the above function; add a conditional or use Integer.MIN_VALUE to handle empty rows if you wish.

edited Jul 25, 2018 at 0:21

answered Jul 24, 2018 at 22:49

ggorlen

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Comments

Tianhao Wang · Accepted Answer · 2018-07-24 22:51:51Z

0

This should work. You reset the min to the first element every time. So you are basically comparing if there is any value smaller than the first one.

    static int[] minimum(int[][] arr){
        int[] result = new int [arr.length];
        for (int i = 0; i < arr.length; i++){
            result[i] = Integer.MAX_VALUE;
            for(int j = 0; j < arr[i].length; j++){
                if(arr[i][j] < result[i]) {         
                    result [i] = arr[i][j];
                }
            }
        }
        return result;
    }

answered Jul 24, 2018 at 22:51

Tianhao Wang

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