we have to find the sum of the elements of the middle row of the matrix, but my code isn't printing anything

Question

public class que2
{
public static int Sum(int[][] nums)
{
int m = nums.length;
int n = nums[0].length;
int sum=0;
for(int i=0;i<m;i++)
{
for(int j=0;i<n;j++)
{
if(i==1)
{
sum += nums[i][j];

}
}
}
return sum;
}

public static void main(String[] args)
{
int[][] nums = {{1,4,9},{11,4,3},{2,2,3}};

System.out.println(Sum(nums));
}

}

Answer 1

It's same. But you took mid row value as 1 directly.

You have only 3 rows so you are taking 1 for middle row value in nums[1][j] . What if you have more rows then find middle row as
int mid = nums.length / 2;
Then find sum by
sum += nums[ mid ] [ j ] ;

This works fine if rows are odd in number. If it is even rows then you need to take sum of mid, mid-1 rows.

See like
nums[][] = { {1, 4, 9}, {11, 4,3}, {2, 2,3} };
sum of mid row(1) is 11+4+3= 18
What if
nums[][] = { {1, 4, 9}, {11,4,3}, {2,3,4}, {2,2,3} };
sum of middle rows 1,2 are 11+4+3=18 and 2+3+4 = 9 ,
then final sum = 18+9=27.

Answer 2

@jayakrishna can you elaborate that more??

I made a new solution to that and it's working but still I wanna know your method.

public class que2
{
public static int Sum(int[][] nums)

{
int n = nums[0].length;
int sum=0;
for(int j=0;j<n;j++)
{
sum += nums[1][j];
}
return sum;
}

public static void main(String[] args)
{
int[][] nums = {{1,4,9},{11,4,3},{2,2,3}};

System.out.println(Sum(nums));
}

}

Answer 3

Got it! Thanks

Answer 4

What do you mean by i==1 condition?
It you need only one row then no need 2 loops..

Directly use i as :
Middle row : you can find by i=nums.length / 2

if nums.length is odd then take i and i-1 rows.
And loop from j=0 to nums[i].length.

Hope it helps...