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Array of vectors containing integers

Posted on 2011-03-08
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Last Modified: 2012-05-11
Hello experts,

I would like to have 2D array containing lists of integers.

I tried this one:

std::vector<int> linesGrid [64, 48];

but it does not compile.

What do I do wrong?

Thank you

panJames
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Question by:panJames
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5 Comments
 
LVL 53

Expert Comment

by:Infinity08
ID: 35069913
If you want to do that with vectors, you'll need a definition that looks somewhat like this :
std::vector<std::vector<int> > linesGrid(64, std::vector<int>(48));

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Author Comment

by:panJames
ID: 35070083
WOW!

I am trying to get my head around it.

1. std::vector<std::vector<int>> linesGrid;

It my understanding: linesGrid is the list of (list of integers)

2. linesGrid(64, std::vector<int>(48));

In my understanding it looks like a function call with two variables where the second one is again a function???

I am so confused here... :(

panJames
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LVL 53

Accepted Solution

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Infinity08 earned 500 total points
ID: 35070300
>> It my understanding: linesGrid is the list of (list of integers)

More accurately : a vector of vectors of ints.


>> In my understanding it looks like a function call with two variables where the second one is again a function???

It's calling the constructor of std::vector, where the first argument is the amount of items you want in the vector, and the second argument is how those items should be initialized.

Refer to :

        http://www.cplusplus.com/reference/stl/vector/vector/
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LVL 34

Expert Comment

by:sarabande
ID: 35070301
the point is that std::vector is a 1d-array. to get a 2d-array you do a vector of row vectors.

Sara

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LVL 34

Expert Comment

by:sarabande
ID: 35070389
actually it is not really a grid like int grid[64][48]  cause each row vector individually could grow or shrink. but if you do an initialisation like infinity08 showed and don't do a push_back or erase on any of the row vectors you pretty well have the same behavior than with a fixed-sized int 2d-array.

Sara
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