I did'nt understand how to find the sum of all submatrix

#1

If li=0 ,and we use arr[li-1][bi] ,here it takes garbage value,please explain me how to find the sum of all sub matrix by the method taught in the video.

#2

You have to impose extra if else conditions and handle that separately. Refer this discussion Sum of all submatrix from a given matrix

#3

I write the code for the program but it shows right answer for 2x2 matrix and it shows wrong answer for 3x3 matrix

#4

You can save your code ide.codingblocks.com and share its link.

#5

https://ide.codingblocks.com/ please check my code it shows wrong answer for 3x3 matrix

#6

#include<bits/stdc++.h>
using namespace std;
int main(){
int n,sum;
cin>>n;
int a[n][n];
for(int i=0;i<n;i++){
for(int j=0;j<n;j++){
cin>>a[i][j];
}
}
for(int i=0;i<n;i++){
sum=0;
for(int j=0;j<n;j++){
sum+=a[i][j];
a[i][j]=sum;
}
}
for(int i=0;i<n;i++){
sum=0;
for(int j=0;j<n;j++){
sum+=a[j][i];
a[i][j]=sum;
}
}
sum=0;
for(int li=0;li<n;li++){
for(int lj=0;lj<n;lj++){
for(int bi=li;bi<n;bi++){
for(int bj=lj;bj<n;bj++){
if(li==0 && lj==0){
sum+=a[bi][bj];
}
else if(li==0 && lj!=0){
sum+=a[bi][bj]-a[bi][lj-1];
}
else if(lj==0 && li!=0){
sum+=a[bi][bj]-a[li-1][bj];
}
else{
sum+=a[bi][bj]-a[bi][lj-1]-a[li-1][bj]+a[li-1][lj-1];
}
}
}
}
}
cout<<sum<<’\n’;
return 0;
}

#7

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