Thread: Quick Explanation

I cant figure how to get the correct output from this code. Can someone explain. Thanks.

Code:

#include <stdio.h>

int main() {
    
int a[] = {8,1,6,3,5,7,2,4,10,9};

int i;

for (i=0;i<10;i++)
    a[i] = a[a[i]-1];
for (i=0; i<10; i++)
    printf("%d ", a[i]);
    
   getchar();
    
    return 0;
     
           }

The answer is 4 4 7 7 5 2 4 7 9 9

Value of array elements is changing on the fly; so write out all intermediate results on paper before evaluating the final expression.

Im just trying to figure out why that prints out the answer. how it works basically. why it prints out that answer. How that array is changed

ok thanks i got it

How does this program work? I cant get the right output from the code

Code:

#include <stdio.h>

int f(int a, int b, int c);

int main() {
    int a = 3, b = 5, c = 2;
    b = f(b, c, a);
    printf("a = %d, b = %d, c = %d\n", a, b, c);
    a = f(c, a, b);
    printf("a = %d, b = %d, c = %d\n", a, b, c);    
    return 0;
}

int f(int a, int b, int c) {
    int t = b+c;
    a = 2*t - 7;
    b = 3*a%13 + 1;
    c = b - a;
    printf("a = %d, b = %d, c = %d\n", a, b, c);
    return a + b + c;
}

The output looks like this

a = 3, b = 10, c = 7
a = 3, b = 20, c = 2
a = 39, b = 1, c = -38
a = 2, b = 20, c = 2 (1 pt each)

Remember that the a, b, and c inside f don't match the a, b, and c inside main -- watch the order that the parameters are given inside the function call.

Should i figure out f first then go though main

Originally Posted by harkroad

Should i figure out f first then go though main

I don't think that makes sense. f is not run independently of main; it is only run when main calls upon it. So you'll have to go through main until yous ee a function call, then work through f (with the specific values that main called it with), then return to main.

I would pay more attention to what laserlight and quzah stated in your first problem, that will still apply for your second. Run through your program on paper, perhaps creating a table for your variables and jot down their values at each step in the table.

Originally Posted by harkroad

The output looks like this

a = 3, b = 10, c = 7
a = 3, b = 20, c = 2
a = 39, b = 1, c = -38
a = 2, b = 20, c = 2 (1 pt each)

Is your test/homework open book, open notes, open professionals living on programming support pages?

Just curious.

Its just a Review for a Test.

the first line get printed bc...

t= 2+3
a= 2*5 - 7 = 3
b= 3* 3%13 +1 = 10
c= 10 - 3 = 7

How does the Second get those values?

Close this Thread I Figured it out thanks