8

#include <stdio.h>

int main()
{
    int i, j,k;
    printf("Enter number of rows:");
    scanf("%d",&k);
    for (i = 1; i <= k; i++)
    {
        for (j = 1; j <= i; j++)
        {
            printf("%c ", 'A' + j - 1);
        }
        printf("\n");
    }
    return 0;
}

9

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter number of rows:");
    scanf("%d",&k);
    for (i = 1; i <= k; i++)
    {
        for (j = 1; j <= i; j++)
        {
            printf("%c ", 'A' + i - 1);
        }
        printf("\n");
    }
    return 0;
}

10

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter number of rows:");
    scanf("%d",&k);
    for (i = k; i>= 1; i--)
    {
        for (j = 1; j <= i; j++)
        {
            printf("%c ", 'A' + i - 1);
        }
        printf("\n");
    }
    return 0;
}

11

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter number of rows:");
    scanf("%d",&k);
    for (i=1;i<=k;i++);
    {
     for (j=1;j<=k-i;j++)
     { 
      printf(" ");
     } 
     for(j=1;j<=(2*i-1);j++)
     {
      printf("*");
     }
     printf("\n");
    }
    return 0;
}

12

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter number of rows:");
    scanf("%d",&k);
    for (i=k;i>=1;i--);
    {
     for (j=1;j<=k-i;j++)
     { 
      printf(" ");
     } 
     for(j=1;j<=(2*i-1);j++)
     {
      printf("*");
     }
     printf("\n");
    }
    return 0;
}

13

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter Number of Rows:");
    scanf("%d",&k);
    
    for (i = 1; i <= k; i++)
    {
        for (j = 1; j <= k - i; j++)
        {
            printf(" ");
        }
        for (j = 1; j <=(2*i-1); j++)
        {
            printf("%d", j);
        }
        printf("\n");
    }
    return 0;
}

14

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter Number of Rows:");
    scanf("%d",&k);
    for (i = k; i >= 1; i--)
    {
        for (j = 1; j <= k - i; j++)
        {
            printf(" ");
        }
        for (j = 1; j <=(2*i-1); j++)
        {
            printf("%d", j);
        }
        printf("\n");
    }
    return 0;
}

15

#include <stdio.h>
int main()
{
    int i, j,k,a=1;
    printf("Enter Number of Rows:");
    scanf("%d",&k);
    for (i = 1; i<=k; i++)
    {
        for (j = 1; j<=i; j++)
        {
         printf("%d",a);
         a++;
        }
        printf("\n");
    }
    return 0;
}

16

#include <stdio.h>
int main()
{
    int i, j,k;
    printf("Enter Number of Rows:");
    scanf("%d",&k);
    for (i = 1; i<=k; i++)
    {
     for (j = 1; j<=i; j++)
     {
      if ((i+j)%2==0)
      {
       printf("1");
      }
      else 
      {
       printf("0"); 
      }
     }
    }
    return 0;
}

17

#include <stdio.h>

int main() {
    int n = 5;

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (i == 1 || i == n || j == 1 || j == n)
                printf("*");
            else
                printf(" ");
        }
        printf("\n");
    }

    return 0;
}

18

#include <stdio.h>

int main() 
{
    int n;
    printf("Enter Number of Rows:");
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) 
    {
        for (int j = 1; j <= i; j++) 
        {
            if (j == 1 || j == i || i == n)
                printf("*");
            else
                printf(" ");
        }
        printf("\n");
    }
    return 0;
}

19

#include <stdio.h>

int main() {
    int n, i, j;
    printf("Enter Number of Rows: ");
    scanf("%d", &n);
    for (i = 1; i <= n; i++) {
        for (j = i; j < n; j++)
            printf(" ");
        for (j = 1; j <= 2 * i - 1; j++)
            printf("*");
        printf("\n");
    }
    for (i = n - 1; i >= 1; i--) {
        for (j = i; j < n; j++)
            printf(" ");
        for (j = 1; j <= 2 * i - 1; j++)
            printf("*");
        printf("\n");
    }
    return 0;
}

20

#include <stdio.h>
int main() {
    int n, i, j;
    printf("Enter n: ");
    scanf("%d", &n);
    for (i = 1; i <= n; i++) 
    {
        for (j = 1; j <= i; j++)
            printf("*");
        for (j = 1; j <= 2 * (n - i); j++)
            printf(" ");
        for (j = 1; j <= i; j++)
            printf("*");
        printf("\n");
    }
    for (i = n; i >= 1; i--) 
    {
        for (j = 1; j <= i; j++)
            printf("*");
        for (j = 1; j <= 2 * (n - i); j++)
            printf(" ");
        for (j = 1; j <= i; j++)
            printf("*");
        printf("\n");
    }
    return 0;
}