Write a program that reads a four digit integer and prints the sum of its digits as an output.

• Simple Implementation
  

#include <stdio.h>
#include <math.h>
int main(){
	int four_digit_num, sum = 0, i, positional;

	scanf("%d", &four_digit_num);

	for(i = 3; i >= 0; i--){
		positional = pow(10, i);
		sum += four_digit_num / positional;
		four_digit_num %= positional;
	}
	printf("%d\n", sum);
	return 0;

}

• Basic Implementation
  

#include <stdio.h>

int main(){
	int four_digit_num, sum = 0, i, positional, j;

	scanf("%d", &four_digit_num);

	for(i = 3; i >= 0; i--){
		positional = 1;
		for(j = 0; j < i; j++){
			positional *= 10;
		}	
		sum += four_digit_num / positional;
		four_digit_num %= positional;
	}
	printf("%d\n", sum);
	return 0;
}

• Advanced Implementation
  

#include <stdio.h>
#include <math.h>

int main(){
	int n_digit_num, sum = 0, positional, n;

	scanf("%d", &n_digit_num);
	
	n = log10(n_digit_num);

	if((n_digit_num >= pow(10, n)) && (n_digit_num < pow(10, n+1))){

		for(; n >= 0; n--){
			positional = pow(10, n);
			sum += n_digit_num / positional;
			n_digit_num %= positional;
		}
		printf("%d\n", sum);
		return 0;
	}

	exit(1);
}

#include <stdio.h>

int main()
{
	int i,j;
	for (i = 0; i < 5; i++) {
		for (j = 4; j > i; j--) printf(" ");
		for (j = 0; j < 2*i+1; j++) printf("*");
		printf("\n");
	}    
	return 0;
}

Write a program that gets a starting principal(A, 원금), annual interest rate(r, 연이율) from a keyboard (standard input) and print the total amount on deposit (예치기간이 지난 뒤 총금액, 원리합계) for the year(n) from 0 to 10. total deposit = A*(1+r)^n

#include <stdio.h>

int main(){
	double a, r, interest = 1;
	int n;
	
	scanf("%lf %lf", &a, &r);

	for(n = 0; n <= 10; n++){
		printf("%d\t%.2f\n", n, a * interest);
		interest *= 1+r;
	}

	return 0;
}

새싹교실/2011/Pixar