小白发问，这个C语言任务该如何编写？求大佬指教

#include

int main(void) {

int n;
int sum = 0, max = -1;
int a[20];

scanf("%d", &n);
for (int i = 0; i < n; i++) {
scanf("%d", &a[i]);
if (a[i] > max) {
max = a[i];
}
}
printf("max=%d,", max);
for (int i = 0; i < n; ++i) {
if (a[i] == max && i > 0) {
sum += a[i - 1];
printf("a[%d]=%d,", i - 1, a[i - 1]);
}
}
printf("sum=%d", sum);
return 0;
}

#include
int fac(int n)
{if(n==0)return 1;
return n*fac(n-1);
}
main()
{ int n,i,j;
scanf("%d",&n);
for(i=0; i<=n; i++)
{ for(j=0; j<n-i; j++)
printf(" ");
for(j=0; j<=i; j++)
printf("%4d",fac(i)/(fac(j)*fac(i-j)));
printf("
");
}
}

#include<stdio.h>

long fac(int i)

{

if(0==i||1==i)

return 1;

return i*fac(i-1);

}

int main()

{

const int sp=4;

int n=5,i,j;

scanf("%d",&n);

for(i=0;i<n;i++)

{

printf("%*ld",sp*(n-i-1)+1,1);

for(j=1;j<=i;j++)

printf("%*ld",sp*2,fac(i)/fac(j)/fac(i-j));

printf("
");

}

return 0;

}