Flood Fill Recursive algorithm

Question

Hello I made use of flood fill recursive algorithm to find the connected cells to each other in an 2D array (Here I am using vectors). But this fails for one boundary test case

#include<iostream>
#include<vector>
using namespace std;
int count = 0;
int max_count = 0;
int min_count = 0;

void floodFillUtil(vector< vector<int> > &a,int i,int j,int m,int n,int prevP,int newN)
{
 if (i<0 || i>= m || j<0 || j>=n)
    return;

 if(a[i][j] != prevP)
    return;

count++;
a[i][j] = newN;
floodFillUtil(a,i+1,j+1,m,n,prevP,newN);
floodFillUtil(a,i-1,j-1,m,n,prevP,newN);
floodFillUtil(a,i-1,j+1,m,n,prevP,newN);
floodFillUtil(a,i+1,j-1,m,n,prevP,newN);
floodFillUtil(a,i+1,j,m,n,prevP,newN);
floodFillUtil(a,i,j+1,m,n,prevP,newN);
floodFillUtil(a,i-1,j,m,n,prevP,newN);
floodFillUtil(a,i,j-1,m,n,prevP,newN);

}

void floodFill(vector< vector<int> > &a,int i,int j,int newN,int m,int n)  {
  int prevP = a[i][j];
  floodFillUtil(a,i,j,m,n,prevP,newN);
 }
 // Driver program to test above function
 int main()
{   int m,n;
    cin>>m>>n;
    vector<vector<int> > a;
    vector<int> b;
    for(int i=0;i<m;i++)
    {for(int j=0;j<n;j++)
      {   int temp;
          cin>>temp;
          b.push_back(temp);  
      }
     a.push_back(b);
     b.clear();
    }
  for(int i=0;i<m;i++)
   for(int j=0;j<n;j++) {
    if (a[i][j] == 1){
       floodFill(a,i,j,2+i,m,m);
       min_count = count ;
       if(min_count > max_count){
         max_count = min_count;
       }
    count=0;
    }
}  
for(int i=0;i<m;i++)
{for(int j=0;j<n;j++)
    cout<<a[i][j]<<" ";
    cout<<endl;}
cout<<max_count;

}

And this is the input test case for which it is failing

8
9
0 1 0 0 0 0 1 1 0
1 1 0 0 1 0 0 0 1
0 0 0 0 1 0 1 0 0
0 1 1 1 0 1 0 1 1
0 1 1 1 0 0 1 1 0
0 1 0 1 1 0 1 1 0
0 1 0 0 1 1 0 1 1
1 0 1 1 1 1 0 0 0

And this is output given by code

0 2 0 0 0 0 2 2 0 
2 2 0 0 3 0 0 0 1 
0 0 0 0 3 0 3 0 0 
0 3 3 3 0 3 0 3 1 
0 3 3 3 0 0 3 3 0 
0 3 0 3 3 0 3 3 0 
0 3 0 0 3 3 0 3 1 
3 0 3 3 3 3 0 0 0 
27

But the output should be 29, for [1,8] [3,8] and [6,8] it is not changing.What must be the problem in the code.

Answer 1

Looks like a typo here:

floodFill(a,i,j,2+i,m,m);

Should be:

floodFill(a,i,j,2+i,m,n);

Unless your matrix is square. It might be worthwhile to abstract the matrix into an object that knows its own dimensions (see here). Then you can pass fewer parameters everywhere.