Count the occurence of a particular digit in a range of number - c++

Question

I was trying to count the number of digit 2 in an range of number (say 2-22, the answer would be 6: 2,12,20,21,22 as 22 contribute twice). This is the code that I came up with, yet it fails to run after value input. Any ideas?
#include <iostream>
#include <cstdio>
using namespace std;
int main(){
int lowerbound,upperbound,sum=0;
int nofNum(int num);
scanf("%d %d",&lowerbound,&upperbound);
for (int i=lowerbound;i<=upperbound;++i){
sum+=nofNum(i);
}
printf("%d",sum);
return 0;
}
int nofNum(int num){
int count=0;
while(num!=0){
if (num%10==2){
count++;
num/=10;
}
}
return count;
}

Answer 1

you are using c not c++. Your mistake is that nofNum wasn't declared before you used it. It has to be declared before the line you use it.
int nofNum(int num);
would declare it.
You will still need to implement it, which you allready did.
alternatively you can move the implementation st. it is above main, where you used it.
EDIT: i just saw you declared it inside main, which is uncommon at best. you really should not do that.
EDIT2:
you messed up that if statement in numOf
int nofNum(int num){
int count=0;
while(num!=0){
if (num%10==2){
count++;
}
num/=10; // may not be inside if, since num would not be adjusted
// if the last digit isnt a 2
}
return count;
}
EDIT3:
you can use input and output streams in c++ to replace scanf and printf:
scanf("%d %d",&lowerbound,&upperbound);
becomes
std::cin >> lowerbound >> upperbound;
and
printf("%d",sum);
becomes
std::cout << sum << std::endl;
Edit4:
suggested form:
// declarations - this is what would belong to the *.h file later on.
int nofNum(int num);
followed by
int nofNum(int num) { /*implementation*/ }
int main(int /*argc*/, char* /*argv*/[]) { /*implementation*/ }
or
// this is valid because we allready heard of nofNum through declaration
int main(int /*argc*/, char* /*argv*/[]) { /*implementation*/ }
int nofNum(int num) { /*implementation*/ }
the upper form doesn't require the declarations because each function allready is implemented before you use them, therefore the compiler allready knows what nofNum is supposed to be.