Bài tập C++ kinh điển

/**
 * Tinh day so Fibonacci KHONG dung phuong phap de quy
 * 
 * @author viettuts.vn
 */

#include <iostream>
  
using namespace std;

/**
 * Tinh so Fibonacci thu n
 *
 * @param n: chi so cua so Fibonacci tinh tu 0
 *           vd: F0 = 0, F1 = 1, F2 = 1, F3 = 2
 * @return So Fibonacci thu n
 */
int fibonacci(int n) {
    int f0 = 0;
    int f1 = 1;
    int fn = 1;
    int i;

    if (n < 0) {
        return -1;
    } else if (n == 0 || n == 1) {
        return n;
    } else {
        for (i = 2; i < n; i++) {
            f0 = f1;
            f1 = fn;
            fn = f0 + f1;
        }
    }
    return fn;
}

/**
 * Ham main
 */
int main() {
 int i;
    cout << "10 so dau tien cua day so Fibonacci: \n";
    for (i = 0; i < 10; i++) {
        cout << fibonacci(i) << " ";
    }
}

#include <iostream>
#include <cmath>

using namespace std;
  
/**
 * check so nguyen to trong C++
 *
 * @author viettuts.vn
 * @param n: so nguyen duong
 * @return 1 la so nguyen so,
 *         0 khong la so nguyen to
 */
int isPrimeNumber(int n) {
    // so nguyen n < 2 khong phai la so nguyen to
    if (n < 2) {
        return 0;
    }
    // check so nguyen to khi n >= 2
    int squareRoot = (int) sqrt(n);
    int i;
    for (i = 2; i <= squareRoot; i++) {
        if (n % i == 0) {
            return 0;
        }
    }
    return 1;
}

/**
 * Ham main
 */
int main() {
 int i;
    cout << "Cac so nguyen to nho hon 100 la: \n";
    for (i = 0; i < 100; i++) {
        if (isPrimeNumber(i)) {
            cout << i << " ";
        }
    }
}

/**
 * Tinh giai thua KHONG dung phuong phap de quy
 * 
 * @author viettuts.vn
 */

#include <iostream>
  
using namespace std;

/**
 * tinh giai thua
 *
 * @author viettuts.vn
 * @param n: so nguyen duong
 * @return giai thua cua so n
 */
long tinhGiaithua(int n) {
 int i;
    long giai_thua = 1;
    if (n == 0 || n == 1) {
        return giai_thua;
    } else {
        for (i = 2; i <= n; i++) {
            giai_thua *= i;
        }
        return giai_thua;
    }
}

/**
 * Ham main
 */
int main() {
    int a = 5;
    int b = 0;
    int c = 10;
    cout << "Giai thua cua " <<  a << "la: " << tinhGiaithua(a) << endl;
    cout << "Giai thua cua " <<  b << "la: " << tinhGiaithua(b) << endl;
    cout << "Giai thua cua " <<  c << "la: " << tinhGiaithua(c) << endl;
}

/**
 * Chuong trinh chuyen doi he co so trong C
 * Bai tap nay su dung bang ASCII de chuyen doi so nguyen thanh kieu ky tu
 * Link tham khao: https://vi.wikipedia.org/wiki/ASCII
 * 
 * @author viettuts.vn
 */

#include <iostream>
  
using namespace std;

const char CHAR_55 = 55;
const char CHAR_48 = 48;

/**
 * chuyen doi so nguyen n sang he co so b
 *
 * @author viettuts.vn
 * @param n: so nguyen
 * @param b: he co so
 */
int convertNumber(int n, int b) {
    if (n < 0 || b < 2 || b > 16 ) {
        printf("He co so hoac gia tri chuyen doi khong hop le!");
        return 0;
    }
    int i;
    char arr[20];
    int count = 0;
    int m;
    int remainder = n;
    while (remainder > 0) {
        if (b > 10) {
            m = remainder % b;
            if (m >= 10) {
                arr[count] = (char) (m + CHAR_55);
                count++;
            } else {
                arr[count] = (char) (m + CHAR_48);
                count++;
            }
        } else {
            arr[count] = (char) ((remainder % b) + CHAR_48);
            count++;
        }
        remainder = remainder / b;
    }
    // hien thi he co so
    for (i = count - 1; i >= 0; i--) {
        printf("%c", arr[i]);
    }
    return 1;
}

/**
 * Ham main
 */
int main() {
    int n = 12;
    printf("So %d trong he co so 2 = ", n);
    convertNumber(n, 2);
    printf("\nSo %d trong he co so 16 = ", n);
 convertNumber(n, 16);
    return 1;
}