Finding the Sum of a Jagged Array

Question

*Homework

I'm trying to add the values in an array. With the sum method I wrote below, the program only works for arrays that are not jagged. If I test a jagged array, I get an IndexOutOfBoundsException. What's the next step I should take to try and make this method work if the array is jagged?

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

Answer 1

Your method is close, but it has a small bug - this

sum += array[j][i];

should be

sum += array[i][j];

Note that your inner loop is iterating over array[i] .

Answer 2

反转索引：

sum += array[i][j];

Answer 3

You are mixing indexes. You are first looping through rows ( i ) , then through columns ( j ), but when you access to the array elements, you are using j for the rows and i for the columns.

It should be:

sum += array[i][j];

Answer 4

Change

sum += array[j][i];

to

sum += array[i][j];