#Write a 'void' function shiftLeft(a,b,c) that takes 3 numbers and shifts them circularly

34 messages · Page 1 of 1 (latest)

reef canopy
#

so I have this question in my homework which I don't really understand.
This is the main function that was given:

int main() {
    int a = 111;
    int b = 32;
    int c = 89;
    for(int i = 0; i < 10; i++){
        shiftLeft(a,b,c);
        cout << "(a,b,c) == (" << a << "," << b << "," << c << ")" << endl;
    }

    return 0;
}

and this is what I could only think off (it's wrong, but maybe it helps)

#include <array>
void shiftLeft(int a, int b, int c) {
    int shift=3;
    int x=shift-1;
    int temp=array[3];
    while (x >= 0 && shift >= 0) {
        array[shift]=array[x];
        x++;
        shift++;
    }
}
mossy stagBOT
#

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flat shore
#

So first, you need probably need to take the three arguments by reference (with an & in the argument definitions)
Basically this means that changes to the arguments also change the variables passed to it

#

;compile

#include <iostream>

void passByValue(int a) {
    a = 5;
}
void passByReference(int& a) {
    a = 5;
}

int main() {
    int c = 10;
    std::cout << c << '\n';
    passByValue(c);
    std::cout << c << '\n';
    passByReference(c);
    std::cout << c << '\n';
}
potent grailBOT
#
Program Output
10
10
5
ZeroPointer#6105 | 185ms | c++ | x86-64 gcc 12.2 | godbolt.org
flat shore
#

Second, you probably don't need to use an array, nor a for loop

reef canopy
flat shore
#

the main was just to be used as an example of pass by reference

#

notice how in one of the function calls, the value of c changed, but in the other it didn't

reef canopy
#

yeah, so that means I have to put the & in the arguments by a, b and c?

flat shore
#

Yep

reef canopy
#

like this, right

void shiftLeft(int& a, int& b, int& c) {
flat shore
#

yep

#

side question, have you written a swap function before?

reef canopy
#

yeah I have that in my book in front of me. That's what I tried to do first, but without success

flat shore
#

so this is just a slightly harder version of the swap function

#

So using the pass by reference, try writing a swap function

reef canopy
#

uhm

&a = &b;
&b = &c;
&c = &a;

I think, sorry if it's wrong. We started learning about this just a few weeks ago

flat shore
#

so for references, you only need to but the & on the argument, afterwords, you use them like any other variable

#

also you are close

#

but the issue is after
a = b
the original value of a is lost so
c = a will have c get the old value of b

reef canopy
#

thats- very confusing

#

i understand what you mean, i just dont understand how I could fix that

flat shore
#

All you need is one extra variable to hold the old value of a

reef canopy
#

so:

x = a;
a = b;
b = c;
c = a;
``` ?
flat shore
#

so close

reef canopy
#

or a = x?

flat shore
#

the first 3 lines are correct

reef canopy
#

hmmm

flat shore
#

you want c to hold the old value of a correct?

reef canopy
#

so c = x?

flat shore
#

yep

reef canopy
#

thank you so much!

#

!solved