Creating a dynamically-allocated array of std::vectors

Question

To create a dynamically-allocated array, I use:

int *x = new int[100];

This creates an array of 100 int elements.

However, if I use:

std::vector<int> *x = new vector<int>(100);

This also creates an array of 100 int elements. But why does it not create an array of 100 vector<int> elements? And how would I go about doing that?

You have used () instead of []. I have added an answer which shows how to dynamically allocate an array of vectors, although I am not sure if that is what you really want. — bialpio
– bialpio, Commented Mar 31, 2015 at 1:02

bialpio · Accepted Answer · 2015-03-31 01:00:09Z

9

In order to achieve what you want you need to do:

std::vector<int> *x = new vector<int>[100];

This will dynamically allocate array of 100 vectors, each vector will be default-constructed.

edited Mar 31, 2015 at 1:00

answered Mar 31, 2015 at 0:54

bialpio

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Mark B · Accepted Answer · 2015-03-31 00:44:58Z

5

If you want to create an 100 vectors each containing 100 integers, just use multiple (nested) vectors:

std::vector<std::vector<int> > x(100, std::vector<int>(100));

answered Mar 31, 2015 at 0:44

Mark B

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Ben · Accepted Answer · 2015-03-31 00:45:19Z

-1

You need to declare the variable as a vector of vectors, rather than a vector of integers.

std::vector<vector<int>> *x = new vector<vector<int>>(100);

answered Mar 31, 2015 at 0:45

Ben

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