1065 : 한수

#include<stdio.h>
void fun(int num){
	int count,a,b,c,n;
	if((num/100)==0)
		count=num;
	else{
		count=99;
		for(int i=100;i<=num;i++){
			n=i;
			a=n%10;
			n/=10;
			b=n%10;
			n/=10;
			c=n%10;
			if((a-b)==(b-c))
				count++;
		}
	}
	if(num==1000)
		count--;
	printf("%d",count);	
}
int main(void){
	int n;
	scanf("%d",&n);
	fun(n);

	return 0;
}

개선

#include<stdio.h>
void fun(int num){
	int count;
	if((num/100)==0)
		count=num;
	else{
		count=99;
		for(int i=100;i<=num;i++){
			if(i%10-(i/10)%10==(i/10)%10-i/100)
				count++;
		}
	}
	printf("%d",count);	
}
int main(void){
	int n;
	scanf("%d",&n);
	fun(n);

	return 0;
}