What is the meaning of map m= {}; in C++?

Question

I was going through a program in C++. I am a beginner, so I was bit confused what's the meaning of this.

Problem was this:

https://www.codechef.com/problems/H1

I saw someone's solution and am confused what the meaning of map<string, int> m= {}; is.

https://www.codechef.com/viewsolution/20124020

Its a null initializer, meaning its making the map start out empty. Theres a few differnt ways/syntax for this. — Mike, Sep 12 '18 at 17:57
Make your question self contained please, don't require people to follow links to grasp what your problem is. — πάντα ῥεῖ, Sep 12 '18 at 17:59
Templates are very useful to write something for everything only once. Here, map is written only once, but applicable for any type, including version you looking at. — huseyin tugrul buyukisik, Sep 12 '18 at 18:06

Maxim Egorushkin · Accepted Answer · 2018-09-13T09:20:11.167

4

std::map<Key, Value> is an associative container that maps keys to values. See std::map for full details.

map<string, int> m = {}; invokes the default constructor of map<string, int>. In fact, = {} part is unnecessary map<string, int> m; does the same thing in a less verbose way.

Also, if both the default constructor and the initializer list constructors are available, = {} calls the default constructor.

edited Sep 13 '18 at 09:20

answered Sep 12 '18 at 17:56

Maxim Egorushkin

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@ShubhamGuptaGgps You may like to get a C++ book. – Maxim Egorushkin Sep 12 '18 at 17:58
Can you suggest me a good one.. sorry if it was a stupid question – Shubham Kumar Gupta Sep 12 '18 at 17:59
@Shubham Gupta Ggps - they are template arguments. They tell `std::map` the *types* to use for key and value. – Jesper Juhl Sep 12 '18 at 17:59
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Good books: https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list – Jesper Juhl Sep 12 '18 at 18:00
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@ShubhamGuptaGgps We keep a list of good books: https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list – πάντα ῥεῖ Sep 12 '18 at 18:00

What is the meaning of map m= {}; in C++?

1 Answers1