SUM OF ALL SUBMATRICES APPROACH 2

#1

#include
//refer notebooks for better notes.
using namespace std;

int main()
{
int row,col;
cout<<“ENTER ROWS AND COLUMNS\n”;
cin>>row>>col;
int arr[100][100];

//
cout<<"ENTER THE ELEMENTS OF THE ARRAY\n";
for(int i=0;i<row;i++)
{
	for(int j=0;j<col;j++)
	{
		cin>>arr[i][j];
	}
}

//now converting this array to prefix sum array;

int prev=0;
for(int i=0;i<row;i++)
{
	prev=0;
	for(int j=0;j<col;j++)
	{
		arr[i][j]=arr[i][j]+prev;
		prev=arr[i][j];
	}
}

for(int i=0;i<row;i++)
{
	prev=0;
	for(int j=0;j<col;j++)
	{
		arr[j][i]=arr[j][i]+prev;
		prev=arr[j][i];
	}
}
//Now our prefix sum array is completed.

//finding sum of all the subarrays-relate to approach 1.

int sum=0,P,Q,M,N;

for(int li=0;li<row;li++)
{
	for(int lj=0;lj<col;lj++)
	{
		for(int bi=li;bi<row;bi++)
		{
			for(int bj=lj;bj<col;bj++)
			{

			
				P=arr[bi][bj];
				Q=arr[li-1][bj];
				M=arr[bi][lj-1];
				N=arr[li-1][lj-1];
				sum=sum+(P-Q-M+N);



			}
		}
	}
}

cout<<"THE SUM OF ALL THE SUBARRAYS OF THE MATRIX IS\n"<<sum;

}

ACCORDING TO WHAT SIR HAS EXPLAINED IN THE TUTORIAL, I’d implemmented the code, but the output is wrong?

So, please check my code.

#2

Please save your code on ide.codingblocks.com and then share its link.

#3
#4

This is the link of the code, please check.

#5

Refer this https://ide.codingblocks.com/s/290506

Add extra conditions for li and lj also, when they are 0. In that case there may be a chance of getting negative index

#6

Yes , I’d put extra conditions for li and lj, but that is also not working.

#7

So, what to do now? ? ? . . .

#8

You did not impose the conditions properly.
Check your code now

#9

Thank you so much pratyush brother.