Sum of all submatrix-Approach-2

#1

Did not understand. Can you explain this over a google meet?

#2

Hi Anjanpreet,
whatever is ur doubt u tell me over here only… i cant come over google meet or anything…
i suggest u to watch video lecture again and try to dry run the code urself… u will get a better insight…

#3

I’am getting the sum as a garbage value when I’am taking size greater than 2.
#include
using namespace std;
void sumSubmatrix(int a[][10],int size)
{
int sum=0;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
a[i][j+1]+=a[i][j];

	}
}
for(int i=0;i<size;i++)
{
	for(int j=0;j<size;j++)
	{
		a[i+1][j]+=a[i][j];
		
	}
}
for(int li=0;li<size;li++)
{
	for(int lj=0;lj<size;lj++)
	{
		for(int bi=li;bi<size;bi++)
		{
			for(int bj=lj;bj<size;bj++)
			{
				sum+=a[bi][bj]-a[li-1][bj]-a[bi][lj-1]+a[li-1][lj-1];
			}
		}
	}
}
cout<<"sum is:"<<sum<<endl;

}
int main()
{
int a[10][10];
int size;
cin>>size;
for(int i=0;i<size;i++)
{
for(int j=0;j<size;j++)
{
cin>>a[i][j];
}

}

sumSubmatrix(a,size);



return 0;

}

#4

Hi @anjanpreetsingh1019
u have to put this condition like this
sum+=a[bi][bj]-(li-1>=0 ? a[li-1][bj] : 0)-(lj-1 >= 0 ? a[bi][lj-1] : 0)+(li-1>=0 && lj-1>=0 ? a[li-1][lj-1] : 0);
corrected code --> https://ide.codingblocks.com/s/639796

#5

hi @anjanpreetsingh1019
i hope its clear now?? u just have to place the check so that value doesn’t go less than 0 as negative index in array will give garbage value only…

#6

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