在屏幕中打印9*9的菱形

#include <stdio.h>
#include <math.h>
int main(){
    /* declaration */
    int x;
    int y;
    int z;
    /* define how many line will be print */
    for (x=1; x<=9; x++)
    {
        /* define how many " " will be print in every line */
        for (y=1; y<=fabs(5-x); y++)
        {
            printf(" ");
        }
        /* define how many "*" will be print in every line */
        for (z = 1; z<= 2*fabs(fabs(5-x)-5)-1; z++)
        {
            printf("*");
        }
        /* finish the line then return */
        printf("\n");
    }
    return 0;
}