Trying to find number of 1s groups in a given 2-dimensional array-CodePudding

I have written a code with recursive technique, but the program shows segmentation fault error. Did I Make any algorithm fault or its just a mistake in my code??

QUESTION:

There are R*C cells in a matrix where R is the number of rows and C is the number of cells in each row. Each cell may or may not have a fruit in it. The presence of a fruit is indicated by 1 and the absence of a fruit in a cell is indicated by 0. The fruits can be of different types and all the fruits belonging to the same type are arranged in adjacent cells (there are eight adjacent cells: top-left, top, top-right, left, right, bottom-left, bottom, bottom-right). The program must print the number of groups of fruits in the matrix.

Boundary Condition(s): 2 <= R, C <= 50

Input:
3 5
1 0 0 0 1
0 1 0 1 1
1 0 0 0 1
 
Output:
2
 
Explanation:
The first group is indicated by the letter F, 
F 0 0 0 1
0 F 0 1 1
F 0 0 0 1
The second group is indicated by the letter S,
1 0 0 0 S
0 1 0 S S
1 0 0 0 S

Input:
5 6
1 0 0 0 1 0 
0 0 1 1 1 0
1 0 0 0 1 0
0 0 0 0 0 0
1 1 0 1 1 1
 
Output:
5

A 1 must be at least adjacent of one 1 of the group to be considered as a member of the group.

My solution:

#include<stdio.h>
#include<stdlib.h>

int R, C, rtnval = 1;

int checkBoundary(int i, int j)
{
    return (i>-1 && j>-1 && i<R && j<C);
}

void checkGroup(int arr[R][C],int i, int j)
{
    if(arr[i][j]==1)
    {
        arr[i][j] = 0;
        //top
        if((checkBoundary(i-1,j)!=0) && arr[i-1][j]==1)
        {
            checkGroup(arr,i-1,j);
            //return;
        }
        //top-left
        if((checkBoundary(i-1,j-1)!=0) && arr[i-1][j-1]==1)
        {
            //arr[i-1
            checkGroup(arr,i-1,j-1);
            //return;
        }
        //top-right
        if((checkBoundary(i-1,j 1)!=0) && arr[i-1][j 1]==1)
        {
            //arr[i-1
            checkGroup(arr,i-1,j 1);
            //return;
        }
        //bottom
        if((checkBoundary(i 1,j)!=0) && arr[i 1][j]==1)
        {
            //arr[i 1
            checkGroup(arr,i 1,j);
            //return;
        }
        //bottom-left
        if((checkBoundary(i 1,j-1)!=0) && arr[i 1][j-1]==1)
        {
            checkGroup(arr,i 1,j-1);
        }
        //bottom-right
        if((checkBoundary(i 1,j 1)!=0) && arr[i 1][j 1]==1)
        {
            checkGroup(arr,i 1,j 1);
        }
        //left
        if((checkBoundary(i,j-1)!=0) && arr[i][j-1]==1)
        {
            checkGroup(arr,i,j-1);
        }
        //right
        if((checkBoundary(i,j 1)!=0) && arr[i][j 1]==1)
        {
            checkGroup(arr,i,j 1);
        }
    }
}


int main()
{
    scanf("%d%d",&R,&C);
    int arr[R][C];
    for(int i=0;i<R;i  ){
        for(int j=0;j<C;j  )
        {
            scanf("%d",&arr[i][j]);
        }
    }
    int group = 0;
    for(int i=0;i<R;i  )
    {
        for(int j=0;j<C;j  )
        {
            if(arr[i][j]==1)
            {
                checkGroup(arr,i,j);
                group  ;
            }
        }
    }
    printf("%d",group);
}

I have tried to follow all the leads to find any 1's and make them 0 so that they cant be mistook for other adjacent 1s.

CodePudding user response：

To begin with, you need to verify that checkBoundary(i, j) returns true before checking if arr[i][j] == 1 (and before attempting to access arr in general).

The same goes for each one of your internal 'if' statements, for example:

if(arr[i-1][j]==1 && (checkBoundary(i-1,j)!=0))

The checkBoundary call must be executed before accessing arr, not after.