1번

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int i=0, j=0,k=1;
   
    for(i=1;i<6;i++){
                   
                     for(j=0;j<i;j++,k++)printf("%2d ",k);

                     printf("\n");
                     }
    system("pause");
   
    return 0;
}

2번

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int i=0, j=0,k=1;
   
    for(i=1;i<6;i++){
                     for(j=0;j<6-i;j++)printf("   ");
                     for(j=0;j<i;j++,k++)printf("%2d ",k);
                     printf("\n");
                     }
    system("pause");
   
    return 0;
}
3번

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int i=0,j=0,k=1;
   
    for(i=0;i<5;i++){
                     for(j=0;j<5-i;j++,k++)printf("%2d ",k);
                     printf("\n");
}
    system("pause");   
    return 0;
}

4번

#include <stdio.h>
#include <stdlib.h>
int main()
{
      int i = 0, l= 0, j,k=1;

      for(i = 5; i > 0; i--){
          for(l= 5- i; l> 0;l--) printf("   ");
          for(j = i + 1; j > 1; j--,k++) printf("%3d",k);

          printf("\n");
      }
    system("pause");
    return 0;
   
    }