CODEWITHSUNDEEP
java
Katie
Katie

Reputation: 452

input the elements in a 2D array in specific manner

Hi I am stuck at this problem, input the elements in a 2D array where number of rows are known but number of columns are not known. But all the rows should have equal number of elements. How can i do this in java

like first input will be number of rows . then lines of input one for each row of the matrix .Each row will contain the same number of columns and each column separated by a space.

I tried this, but it is not working

System.out.println("Enter the number of rows");
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int [] [] matrix = new int [N][N];
        int row=0;
        int col =0;
        while(sc.hasNextInt() && N<=col)
        {System.out.println("Enter the elements");
            matrix[row][col++]=sc.nextInt();
            col++;
        }
        for(int i=1; i<=N; i++)
        {
            for(int j =0; j<=col;j++)
            {System.out.println("enter the elements");
                matrix[i][j]=sc.nextInt();
            }
        }

Upvotes: 0

Views: 57

Answers (2)

Cinnam
Cinnam

Reputation: 1922

If you don't know the number of columns, you can do something like this:

    Scanner sc = new Scanner(System.in);

    int rows = sc.nextInt();
    sc.nextLine(); // nextInt() didn't consume the newline so we do it here
    int[][] matrix = new int[rows][];

    for (int i = 0; i < rows; i++) {

        String line = sc.nextLine();
        String[] valueStrings = line.split("\\s+");

        matrix[i] = new int[valueStrings.length];

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

            matrix[i][j] = Integer.parseInt(valueStrings[j]);
        }

    }

    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < matrix[i].length; j++) {
            System.out.print("" + matrix[i][j] + " ");
        }
        System.out.println();
    }

Input:

3
1 2 3 4
5 6 7 8
9 0 1 2

Output:

1 2 3 4 
5 6 7 8 
9 0 1 2

edit: fixed the wrong nesting

Upvotes: 1

Manos Nikolaidis
Manos Nikolaidis

Reputation: 22254

You seem to want to read a matrix with known number of rows and columns. This should do that :

Scanner sc = new Scanner(System.in);
int N = sc.nextInt();
int[][] matrix = new int[N][N];

System.out.println("Enter the elements");
for (int row = 0; row < N; ++row) {
    for (int col = 0; col < N; ++col) {
        matrix[row][col] = sc.nextInt();
    }
}

In your attempt you need to think more about why you are incrementing col twice, why you are comparing for less or equal to N and why the for loop starts from 1 and not 0.

Upvotes: 0

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