11.10 Lab4

introduction-to-computer-science-laboratory-4.pdf

Introduction to Computer Science

Laboratory 4

November 10, 2024

Write the expression result and how it affects the variables involved.
- (a) ( a++ > 3 && 4 == 4 ) with ( a = 3 )
This condition is false, because first do the determination of a > 3 which is false. Then Let a = a + 1, then a = 4 * (b) ( ++a > 3 && 4 == 4 ) with ( a = 3 )

This condition is true, because first Let a = a + 1, then a = 4, then do the determination of a > 3 which is true. Also 4 == 4 is true. * (c) ( a++ || j >= 0 ) with ( a = 0 ) and ( j = 0 )

Only a = a + 1, then a = a + 1, but the program doesn't determine whether j >= 0. Since the previous condition has been already true. * (d) ( j >= 0 || a++ ) with ( a = 0 ) and ( j = 0 )

Only j >= 0, then this condition will be true, but the program doesn't run a++. Since the previous condition has been already true. * (e) ( a++ && --j >= 0 ) with ( a = 0 ) and ( j = 1 )

First do the determination of 0 which is false since a = 0 (then a = a + 1). Then j will not change. * (f) ( 1 > 0 || 1/0 )

Only determine 1 > 0 is true * (g) ( 1/0 || 1 > 0 )

Error, doesn't run. * (h) ( (a = 7) > 0 ) with ( a = -3 )

Always true * (i) ( (a = 7) > 0 && (b = 44) > 44 ) with ( a = -3 ) and ( b = 150 )

Always false * (j) ( (a = 7) > 0 || (b = 44) > 44 ) with ( a = -3 ) and ( b = 150 )

Always true * (k) ( 7 - (a = (b + 1)) == 1 ) with ( a = 3 ) and ( b = 5 )

Always true

Write the output of the following two C programs.\

#include <stdio.h>
int main() {
    int i = 0;
    int j = 5;
    j = j++;
    while (i < j) {
        i++;
        printf("%i \n", i);
    }
    return 0;
}
/* outputs:
1
2
3
4
5*/

#include <stdio.h>
int main() {
    int i = 0;
    int j = 5;
    j = ++j;
    while (i < j) {
        i++;
        printf("%i \n", i);
    }
    return 0;
}
/* outputs:
1
2
3
4
5
6*/

Note that the only difference is j = j++; and j = ++j;

For the first one, first let j = j, since j = 5, then 5 will be signed to j, after that, j will plus one, but this operation has no effect on the assignment of j = 5

Solve all the exercises present in the 4th tutorial.

Write a C program that asks the user for an integer ( n ) and tells if ( n ) is a perfect number or not. A number is perfect if it is equal to the sum of its divisors, excluding itself. (e.g., 6 is perfect because \( 6 = 1 + 2 + 3 \)).

#include <stdio.h>

int main() {
    int number, divisor, sum = 0;
    printf("Please enter a number, then I will tell you whether it is a perfect number:");
    scanf("%d", &number);
    for(divisor = 1; divisor < number; divisor++) {
        if (number % divisor == 0) {
            sum = sum + divisor;
        }
    }
    if (sum == number) 
        printf("Yes! %d is a perfect number!", number);
    else 
        printf("No! %d is not a perfect number!", number);
    return 0;
}

Write a C program that asks for two integers ( a ) and ( b ) and then prints the Least Common Multiple (LCM) between ( a ) and ( b ). (e.g., with \( a = 4 \) and \( b = 6 \), the output should be 12).

#include <stdio.h>

int main() {
    int a, b, LCM;
    printf("Please enter two numbers, then I will tell you the LCM of them:");
    scanf("%d %d", &a, &b);
    for(LCM = 1; LCM <= a*b; LCM++) {
        if ((LCM % a == 0) && (LCM % b == 0)) {
            printf("The LCM of %d and %d is %d!", a, b, LCM);
            break;
        }
    }
    return 0;
}

Write a C program that asks for two integers ( x ) and ( y ) and then prints the result of ( x^y ).

#include <stdio.h>

int main() {
    int x, y, result = 1;
    printf("Please enter x and y, then I will tell you x^y:");
    scanf("%d %d", &x, &y);
    for(int times = 1; times <= y; times++) {
        result = result * x;
    }
    printf("%d^%d=%d", x, y, result);
    return 0;
}

Write a C program that, given an integer ( n ), prints out all the perfect numbers less than or equal to ( n ).

#include <stdio.h>

int main() {
    int n, number, divisor, sum = 0;
    printf("Please enter n, then I will tell you all the perfect numbers less than or equal to n:");
    scanf("%d", &n);
    for (number = 1; number <= n; number++) {
        sum = 0;
        for (divisor = 1; divisor < number; divisor++) {
            if (number % divisor == 0)
                sum = sum + divisor;
        }
        if (sum == number) 
            printf("%d ", number);
    }
    return 0;
}

Write a C program that asks the user for an integer ( n ) and tells if the number is automorphic. A number is automorphic if its square ends in the same digit. For example, 25 is automorphic because both 25 and 625 (\( 25^2 \)) end in 5.

#include <stdio.h>

int main() {
    int n, square;
    printf("Please enter n, then I will tell you if the number is automorphic:");
    scanf("%d", &n);
    square = n * n;
    if ((square % 10) == (n % 10))
        printf("Yes, it is automorphic");
    else 
        printf("No, it is not automorphic");
    return 0;
}

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