Creating multiple structs in one for loop

Question

So I have a loop that goes something like

for (r = 0; r < k; r++) {
    pair p = {r, D[r]};
    queue.push(p);
}

where pair is defined as

struct pair {
    int u;
    float d;
}

Is this a legal way to create k pairs and push them onto a priority queue? Do the pairs still exist on the queue in their original form even though p gets overwritten each time? Or does each pair that's already on the queue get automatically updated to the new value of p, resulting in a queue full of identical copies of the same pair?

Thanks!

NPE · Accepted Answer · 2012-11-28 19:53:00Z

4

The code is fine.

p gets copied into the queue; it doesn't matter what happens to the original after the copy is made.

answered Nov 28, 2012 at 19:53

NPE

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Comments

user1599559 · Accepted Answer · 2012-11-28 20:05:18Z

1

Yes, your code works as is. The default copy constructor of p is called, and a copy is pushed into queue. However, you can simplify your code a bit by adding a constructor. If you define pair as:

struct pair {
    pair(int u_, float d_) : u(u_), d(d_){}
    int u;
    float d;
};

Then in your loop, you can simply do:

for (r = 0; r < k; r++) {
    queue.push_back(pair(r, D[r]));
}

That way, it is a bit more clear that you are intentionally pushing a copy. Also, make sure you have a ; after the end of your struct declaration! If you forget, you can end up with some mysterious compiler errors.

answered Nov 28, 2012 at 20:05

user1599559

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