Consider the following method, sumRows, which is intended to traverse all the rows in the two-dimensional (2D) integer array num and print the sum of all the elements in each row.
public static void sumRows(int[][] num)
{
for (int[] r : num)
{
int sum = 0;
for (int j = 0; j < num.length; j++)
{
sum += r[j];
}
System.out.print(sum + " ");
}
}
For example, if num contains {{3, 5}, {6, 8}}, then sumRows(num) should print "8 14 ".
The method does not always work as intended. For which of the following two-dimensional array input values does sumRows NOT work as intended?
A. {{10, -18}, {48, 17}}
B. {{-5, 2, 0}, {4, 11, 0}}
C. {{4, 1, 7}, {-10, -11, -12}}
D. {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}
E. {{0, 1}, {2, 3}}

It shouldn't be "j < num.length" as the iteration of the inner loop will be based on the length of the row number of the two dimensional array. The inner loop is expected to traverse through the every column of the same row in the two dimensional array and sum up the number. To fix this error, we can change it to

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

MrRoyal MrRoyal · Answer 2 · 2021-12-07T07:24:46+01:00

The sumRows method adds up all elements in each row, and prints the calculated sum.

The sumRows method would not work for input values (c) {{4, 1, 7}, {-10, -11, -12}}

In the inner loop of the sumRows method, we have

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

The above loop iterates from 0 to one less than the number of columns in the array.

Take for instance, {{10, -18}, {48, 17}} has 2 rows, and 2 columns.

So, the iteration would be for elements at indices 0 and 1.

However, the array {{4, 1, 7}, {-10, -11, -12}} has 3 rows and 2 columns

So, the iteration would be for elements at indices 0 and 1; leaving the element at index 2

Hence, the sumRows method would not work for input values (c) {{4, 1, 7}, {-10, -11, -12}}