C :

#include<stdio.h>

int main()
{
    printf("      *\n");
    printf("      **\n");
	printf("*     ***\n");
	printf("**    ****\n");
	printf("**************\n");
	printf("**    ****\n");
	printf("*     ***\n");
	printf("      **\n");
	printf("      *");
	return 0;
} 

C++ :

#include<stdio.h>

int main()
{
	printf("      *\n");
	printf("      **\n");
	printf("*     ***\n");
	printf("**    ****\n");
	printf("**************\n");
	printf("**    ****\n");
	printf("*     ***\n");
	printf("      **\n");
	printf("      *\n");
	return 0;
}