Kiểm tra giữa môn - assignment - 60 phút - Khóa học lập trình C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char *argv[]) {
	//Bai 1:
	int N, mod;
	long int total = 0;
	
	printf("\nNhap vao so nguyen N = ");
	scanf("%d", &N);
	
	//N = 123 -> N % 10 -> 3 + total, N = N / 10 = 12 ===> Loop
	while(N > 0) {
		mod = N % 10;
		total += mod;
		//total += N % 10;
		
		N = N / 10;
	}
	printf("\nTong = %d", total);
	
	//Bai 3:
	//Giai phap -> luu so nguyen cuc to -> 3957434658734658734658347563485645896754897923648
	char s[100];
	int i, length, value;
	
	printf("\nNhap so nguyen bat ky: ");
	fflush(stdin);fflush(stdout);
	gets(s);
	
	length = strlen(s);
	
	//So nguyen chia het cho 3: Tong cac so cua -> cung chia het cho 3
	//12, 123, 27, 21, ...
	total = 0;
	for(i=0;i<length;i++) {
		/***
			Ep kieu '1' (char) -> 1 (int), '2' (char) -> 2 (int), '0' (char) -> 0 (int), ...
			ASCCI: '0' -> 48, '1' -> 49, '2' -> 50, '3' -> 51, '4' -> 52, '5' -> 53, ...
			value = s[i](char) ('5') = s[i] - '0' = '5' - '0' = 53 - 48 = 5 (int)
		*/
		value = s[i] - '0';//'1' -> 49, '0' -> 48 : '1' - '0' = 1 (int)
		total += value;
	}
	
	printf("\nTotal = %d", total);
	
	if(total % 3 == 0) {
		printf("\nSo nguyen %s chia het cho 3", s);
	} else {
		printf("\nSo nguyen %s khong chia het cho 3", s);
	}
	
	return 0;
}