fail using hash_map<vector<int>,string>, why ?

Answer 1

First, make sure that the header that you include really exists on your installation.

Second, hash_map is in the stdext namespace, make sure you make this name visible via specifying it explicitly as stdext::hash_map, or via a using directive.

Third, where are the template arguments for your hash_map in your code? I only see hash_map and not hash_map<vector<int>,string>.

Fourth, I'm not sure if std::vector can be used as a hash key for a hash map just like this. You need to define a hash function for your key (via implementing a hash_compare function object and passing it to the hash_map as third template parameter). Anyway storing these vectors by value is hardly a good idea, instead you should probably consider using pointers to these vectors as keys.

Answer 2

Even if it works, I smell fish... Under what circumstance do you want to use a vector-of-ints as a key to retrieve a string attribute from a hash-map?

Sounds like poor/no design to me... just think about the expense of calculating all those hashCodes for a start.

Answer 3

There are multiple errors in the code :

1. int _tmain(int argc, TCHAR argv[])

   Although you are using the precompiled file provided by Visual C++, the pre compiled header file "stdafx.h" is not included.

2. Specify the namespace which is being used using namespace std; using namespace stdext;

3. hash_map is used incorrectly : http://www.sgi.com/tech/stl/hash_map.html

Answer 4

To compare the keys, <,==,> operators should be defined. The find() function here doesn't know how to compare the keys.

Answer 5

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 echo 'Google';
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