C++ how to change struct value?

Question

struct command
{
    char name[20];
    int amount;
};

int main()
{
    command n[10];

    // Im sorting array in ascending order by the amount here
    int temp;
    for(int i=0; i<10; i++) 
    {
        for(int j=0; j<10-1; j++)
        {
            if(n[j].amount>n[j+1].amount)
            {
                temp=n[j].amount;
                n[j].amount=n[j+1].amount;
                n[j+1].amount=temp;
            }
        }
    }
}

Problem is, this code sorts out only n[].amount, but I need to sort out name together with it. For example:

n[1].name="fff", n[1].amount=4, n[2].name="ggg", n[2].amount=1

and after sorting them out in ascending order it should be like this:

n[1].amount=1, n[1].name="ggg", n[2].amount=4, n[2].name="fff"

but my code only sorts out n[].amount. Sorry for the poor explanation, I'm really new to programming

Why you are using `char` arrays to represent strings instead of `std::string`? — Algirdas Preidžius, Jun 13 '17 at 14:57
You are only swapping `amount`. You need to swap the entire struct. — 001, Jun 13 '17 at 14:57
Essentially this: https://stackoverflow.com/questions/1380463/sorting-a-vector-of-custom-objects — NathanOliver, Jun 13 '17 at 14:58
@NathanOliver Yup. Too bad I can't see the `std::tie` comparison trick there, but I'd much rather add it to the big Q rather than here. — Bartek Banachewicz, Jun 13 '17 at 14:59

score 0 · Accepted Answer · edited Jun 13 '17 at 17:48

0

Since this is C++, you should be able to do the following:

command temp = n[j];
n[j] = n[j+1];
n[j+1] = temp;

but since this is 2017, you might as well do the following:

std::swap(n[j], n[j+1]);

edited Jun 13 '17 at 17:48

NathanOliver

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answered Jun 13 '17 at 14:57

Mike Nakis

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2

So.. `std::swap(n[j], n[j+1]];`? – NathanOliver Jun 13 '17 at 15:01
@NathanOliver well, if the OP was using `std` I would expect them to use an actual vector. The OP is likely a student learning very basic old-style C++ without `std`, so I do not think it is a good idea to suggest using `std`, nor is it a good idea to close the question as a duplicate of one which was about `std`. – Mike Nakis Jun 13 '17 at 15:05
Remember, answers aren't just for the OP, they are for all the others that find this. Why not show how you can do it with both? Or at least say well, you can do this to fix it, but the idiomatic way is and show them that. Also, I didn't close the Q. – NathanOliver Jun 13 '17 at 15:10
@NathanOliver well, you are right. I fixed that. – Mike Nakis Jun 13 '17 at 17:47

C++ how to change struct value?

1 Answers1