CODEWITHSUNDEEP
c++arraysqueue
Zhang LongQI
Zhang LongQI

Reputation: 494

how can i store array to queue in c++

queue < int* > qq;

for (int i = 0; i < N; i++) {
    int cc[2] = {i, i + 1};
    qq.push(cc);
}

The N is large but not Exact so I want use queue. I want to store many arrays to queue,but the arrays which qq stored are the same one. How can I do it?

Upvotes: 2

Views: 11249

Answers (3)

Israel Unterman
Israel Unterman

Reputation: 13510

You push each time the same address, namely, cc. You need to dedine a struct holding the two values, like so:

struct CC {
    int x, y;
    CC(int _x, int _y) : x(_x), y(_y) {}
}

queue<CC> qq;

and then..

qq.push(CC(i, i + 1));

Upvotes: 0

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

Your code won't work. Each cc has the same stack location in the loop.

You need to allocate the cc array in the heap, perhaps using int *cc = new int[2]; (but then you need to delete it later).

A better way would be to have cc declared as a std::vector or std::array or std::tuple (in C++11).

Upvotes: 7

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361322

What you're doing is syntactically right, but conceptually wrong. You're inserting local array which gets created in each iteration and destroyed at the end of the iteration; that leaves qq in an unusable state. Outside the loop, dereferencing any element of qq would invoke undefined behavior.

Use std::vector:

std::queue<std::vector<int>> qq;

for (int i = 0; i < N; i++) {
    std::vector<int> cc{i, i + 1};
    qq.push(cc);
}

Upvotes: 3

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