practice hsc 1

#include <stdio.h>

int main()
{
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);

    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j<=i; j++)
        {
            printf("%d", j);
        }
        printf("\n");

    }

    return 0;
}



/*
Enter a number: 4
1
12
123
1234
*/

---------------------------------------------------

/**

Find if a number is prime (without function)

**/

#include <stdio.h>

int main()
{
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);

    int flag = 1;
    for(int i = 2; i < n; i++)
    {
        if(n % i == 0)
        {
            printf("%d is not prime\n", n);
            flag = 0;
            break;
        }
    }
    if(flag == 1)
    {
        printf("%d is a prime\n", n);
    }

    return 0;
}



/*

Enter a number: 20
20 is not prime

*/

---------------------------------------------------

/**

Find if a number is prime (with function)

**/

int isPrime(int n)
{
    for(int i = 2; i < n; i++)
    {
        if(n % i == 0)
        {
            return 0;
        }
    }
    return 1;
}


#include <stdio.h>

int main()
{
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);

    if(isPrime(n))
    {
        printf("%d is a prime\n", n);
    }
    else
    {
        printf("%d is not a prime\n", n);
    }

    return 0;
}



/*

Enter a number: 5
5 is a prime

*/

---------------------------------------------------

/**

print primes from 2 to N (with function)

**/

int isPrime(int n)
{
    for(int i = 2; i < n; i++)
    {
        if(n % i == 0)
        {
            return 0;
        }
    }
    return 1;
}


#include <stdio.h>

int main()
{
    int n;
    printf("Enter n: ");
    scanf("%d", &n);

    for(int i = 2; i<=n; i++)
    {
        if(isPrime(i))
        {
            printf("%d ", i);
        }
    }

    return 0;
}



/*

Enter a number: 5
5 is a prime

*/

---------------------------------------------------

/**

print primes from 2 to N (without function)

**/

************* H W *************


---------------------------------------------------

/**

find GCD

**/



#include <stdio.h>

int main()
{
    int a, b;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);

    int min, gcd;

    if(a <= b) min = a;
    else min = b;

    for(int i = 1; i<=min; i++)
    {
        if(a % i == 0 && b % i == 0)
        {
            gcd = i;
        }
    }

    printf("GCD: %d\n", gcd);

    int lcm = (a * b) / gcd;

    printf("LCM: %d\n", lcm);

    return 0;
}



/*

Multiples:
3 = 3, 6, 9, 12, ...


Divisors:
30 = 1 . 30
   = 2 . 15
   = 5 . 6



GCD Greatest Common Divisors

30 20

30 = 1, 2, 5, 6, 10, 15, 30
20 = 1, 2, 5, 10, 20

Choto number er divisor boro number er o divisor kina => true: common divisor


*/