I am trying to print the maximum sum of a row from a 2d-array but it is looping the printing info I am not sure why since my minimum sum method is the same and that one is working fine as in not looping the print line. Also, the reason why I am not just printing it out in the main is that I have to print the row it is in.

UPDATE: SOLVED

The output that's happening with the maximum sum:

row 1 has the highest sum: 200.0
row 2 has the highest sum: 1990.0
row 4 has the highest sum: 2200.0
row 5 has the highest sum: 2250.0

the output I want:

row 5 has the highest sum: 2250.0

public static double findMaximum(double [][] arr) {
    double maxSum = Double.MIN_VALUE;

    for (int i= 0; i < arr.length; i  ) {
        double sum = 0.0;

        for (int j = 0; j < arr[i].length; i  ) {
            sum  = arr[i][j];
        }
             
        if (maxSum < sum) {
            maxSum = sum;
            System.out.println("row "   (i   1)   "has the highest sum is "   maxSum);
        }  
    }

    return maxSum;

public static double findMin(double [][] arr) {
    double minSum = Double.MAX_VALUE;

    for (int i = 0; i < arr.length; i  ) {
        double sum = 0.0;

        for (int j = 0; j < arr[i].length; j  ) {
            sum  = arr[i][j];
        }

        if (minSum > sum) {
            minSum = sum;
            System.out.println("row "   (i  1)   " has the lowest sum : "   minSum);
        }
    }

    return minSum;
}

CodePudding user response：

All you need is just retrieve a row index along with sum of the row.

public static void main(String[] args) {
    double[][] arr = {
            { 9, 10, 11, 12 },
            { 5, 6, 7, 8 },
            { 1, 2, 3, 4 } };

    Pair maxSum = findSum(arr, Pair.SORT_BY_SUM_ASC.reversed());
    Pair minSum = findSum(arr, Pair.SORT_BY_SUM_ASC);

    System.out.format(Locale.ENGLISH, "row %d has the highest sum is %.2f\n", maxSum.row   1, maxSum.sum);
    System.out.format(Locale.ENGLISH, "row %d has the lowest sum is %.2f\n", minSum.row   1, minSum.sum);
}

private static final class Pair {

    public static final Comparator<Pair> SORT_BY_SUM_ASC = Comparator.comparingDouble(pair -> pair.sum);

    public final int row;
    public final double sum;

    public Pair(int row, double sum) {
        this.row = row;
        this.sum = sum;
    }

}

public static Pair findSum(double[][] arr, Comparator<Pair> comparator) {
    return IntStream.range(0, arr.length)
                    .mapToObj(row -> new Pair(row, Arrays.stream(arr[row]).sum()))
                    .min(comparator).orElseThrow();
}

CodePudding user response：

Here is how you can find the max without using streams which I would think you can't do (since this may be for homework). This can also be applied to your findMinimum method. Rows start with 1.

What you can do is declare a record which is an immutable class which is perfect for situations like this.

record Result(int row, double sum){};
    
double[][] data = { { 12.0, 23.8, 44.2 }, { 45, 2, 3.8 },
        { 48.6, 22.5,17.9}, { 1, 2, 3, 4, 5, 6 } };

Result results = findMaximum(data);
System.out.printf("Maximum sum = %.2f in row %d%n", results.sum, results.row);

prints

Maximum sum = 89.00 in row 3

The method

public static Result findMaximum(double [][] arr) {
    double maxSum = Double.MIN_VALUE;
    int maxRow = 0;
    for (int i = 0; i < arr.length; i  ) {
        double sum = 0;
        double[] row = arr[i];
        for (double item : row) {
            sum  = item;
        }
        if (maxSum < sum) {
            maxSum = sum;
            maxRow = i 1;
        }   
    }

    return new Result(maxRow, maxSum);
}

If you are allowed to use streams, this will work.

• stream indices of rows
• map the row and sum to a Result object
• find the maximum by check the sum of the just created object
• and return an optional.

Optional<Result> opt = IntStream.range(0, data.length)
                   .mapToObj(i -> new Result(i 1, Arrays.stream(data[i]).sum()))
                   .max(Comparator.comparing(Result::sum));

if (opt.isPresent()) {
   Result results = opt.get();
   System.out.printf("Maximum sum = %.2f in row %d%n", results.sum, results.row);
}