大家可否帮个忙，就是一个菱形

#include<stdio.h>
void main(void)
{
// 1
int val,num;
char a;
//2
int f1,f2,f3,f4,f;
printf("Please Enter Last Number : ");
while(1)
{
while(scanf("%d",&num) != 1)
{
while((a=getchar()) != '\n');
printf("Enter not a number , Please ReEnter : ");
}
if(num<=0)
printf("Num <= 0 , Please ReEnter : ");
else
break;
}
for(f1=0;f1<num*2-1;f1++)
{
if(f1>=num)
f=num-(f1-num+2);
else
f=f1;
{
for(f2=0;f2<num-f-1;f2++)
printf(" ");
for(f3=1;f3<f+2;f3++)
printf("%d",f3);
for(f4=f;f4>=1;f4--)
printf("%d",f4);
printf("\n");
}
}
}