#include <stdio.h>
#include <conio.h>
void main()
{
int n;
int dem=0;
int x=0;
int s=0;
int p=0;
printf("nhap vao mot so: ");
scanf("%d",&n);
while (n!=0)
{
x=n%10;
n=n/10;
s=s+x;
if (x%2==0)
{
p+=x;//p=p+x;
dem++;
}


}
printf("tong cac chu so xuat hien trong n: %d\n",s);
printf("tong cac chu so chan xuat hien trong n: %d\n",p);
printf("trung binh cong cac chu so chan xuat hien trong n: %0.2f",1.0*p/dem);
getch();
}


moi nguoi thu xem minh lam co dung khong nhe.

#include <stdio.h>
void main()
{
int d,m,y;
printf("nhap ngay:");
scanf("%d",&d);
printf("nhap thang");
scanf("%d",&m);
printf("nhap nam");
scanf("%d",&y);
int flag=0;//co
switch(m)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
if(d<1||d>31)
flag=1;break;
case 4:
case 6:
case 9:
case 11:
if(d<1||d>30)
flag=1;break;
case 2:
if(y%400==0||y%4==0&&y%100!=0)
{
if(d<1||d>29)
flag=1;
}
else if(d<1||d>28)
flag=1;break;
default:flag=1;
}// dong switch
if(flag==1)
{
printf("Nhap khong dung");
return;
}
/*cau 5*/
int count =0;//i=1;
for (int i=1;i<m;i++){//bo for,thay while(i<m){
if(i==1||i==3||i==5||i==7||i==8||i==10||i==12)
count=count+31;
else
if(i==4||i==6||i==9||i==11)
count=count+30;
else
if(i==2)
{
if(y%400==0||y%4==0&&y%100!=0)
count=count+29;//count+=29
else
count=count+28;
}
}//dong for, hoac co the i++;}//dong while
count=count+d;
printf("Ngay thu %d",count);
}/*dong ham main*/