Convert nested loops into recursion in C, patterns using recursion

 #include <stdio.h>

int main()

{

    int r,c, n,nr,nc,c1=1,c2=1;

    scanf("%d", &n);

    nr=2*n-1;

    nc=2*n-1;

    for(r=1;r<=nr;r++)

    {

        for(c=1;c<=nc;c++)

        {

            if(c<c1||c>c2)

                printf(" ");

            else

                printf("*");

        }

        if(r<n)

        {

            c1++;

            c2=c2+2;

        }

        else

        {

            c1--;

            c2=c2-2;

        }

        printf("\n");

    }

}

Consider a nested loop as shown above..

First i tried converting inner c loop into recursion and i got this code below

#include <stdio.h>

void loop(int c,int nc,int c1,int c2)

{

    if(c>nc)

        return;

    if(c<c1||c>c2)

        printf(" ");

    else

        printf("*");

    loop(c+1,nc,c1,c2);

}

int main()

{

    int r,c, n,nr,nc,c1=1,c2=1;

    scanf("%d", &n);

    nr=2*n-1;

    nc=2*n-1;

    for(r=1;r<=nr;r++)

    {

        loop(1,nc,c1,c2);

        if(r<n)

        {

            c1++;

            c2=c2+2;

        }

        else

        {

            c1--;

            c2=c2-2;

        }

        printf("\n");

    }

}

Now further converting outer r loop the program would like this as shown below

#include <stdio.h>

void loop(int c,int nc,int c1,int c2)

{

    if(c>nc)

        return;

    if(c<c1||c>c2)

        printf(" ");

    else

        printf("*");

    loop(c+1,nc,c1,c2);

}

void pattern(int r,int n,int c1,int c2)

{

    if(r>2*n-1)

        return;

    loop(1,2*n-1,c1,c2);

    if(r<n)

    {

        c1++;

        c2=c2+2;

    }

    else

    {

        c1--;

        c2=c2-2;

    }

    printf("\n");

    pattern(r+1,n,c1,c2);

    

}

int main()

{

    int r,c, n,nr,nc,c1=1,c2=1;

    scanf("%d", &n);

    nr=2*n-1;

    nc=2*n-1;

    pattern(1,n,c1,c2);

}

Further can be improved as

#include <stdio.h> void loop(int c,int nc,int c1,int c2) { if(c>nc) return; if(c<c1||c>c2) printf(" "); else printf("*"); loop(c+1,nc,c1,c2); } void pattern(int r,int n,int c1,int c2) { if(r>2*n-1) return; loop(1,2*n-1,c1,c2); if(r<n) { printf("\n"); pattern(r+1,n,c1+1,c2+2); } else { printf("\n"); pattern(r+1,n,c1-1,c2-2); } } int main() { int r,c, n,nr,nc,c1=1,c2=1; scanf("%d", &n); nr=2*n-1; nc=2*n-1; pattern(1,n,c1,c2); }