Modern C++ is amazing with many great features. In C++, STL Standard Template Library has many algorithms for some operations like searching, counting, and manipulation of ranges and their elements. In this post you can learn C++ feature called std::map that you can map pair elements with an appropriate C++ IDE and compiler. One of its powerful modifiers of std::map is insert(). In this post we will explain how to use the C++ std::map insert() function.
Table of Contents
What is std::map in Modern C++?
std::map is a sorted associative container found in the C++ Standard Template Library (STL) that stores key-value pairs with unique keys. Each member has a unique key value and a mapped value. Two or more mapped values cannot have the same key values – the key needs to be unique. When using std::map, key values are sorted by using the comparison function compare. Compare.
Here is the Syntax for the std::map (Since C++17);
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namespace pmr { template< class Key, class T, class Compare = std::less<Key> > using map = std::map< Key, T, Compare, std::pmr::polymorphic_allocator<std::pair<const Key, T>> >; } |
Is there a simple Example of how to use Insert in std::map in Modern C++?
The insert method of std::map can be used as given in this syntax below,
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std::pair<iterator, bool> insert( const value_type& value ); |
This allows us to have string and integer values in our map. If you want to make string values key values that will be sorted, you can use std::map as below:
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std::map< std::string, int > mp; |
if you want, you can directly declare members of this map as below,
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std::map< std::string, int > mp{ {"Jim", 182}, {"David", 185}, {"Ian", 183} }; |
Is there a complete example of how to use Insert in std::map in Modern C++?
Here is a full example.
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#include <iostream> #include <map> #include <tchar.h> #include <string> int _tmain(int argc, _TCHAR* argv[]) { std::map< std::string, int > mp; auto i = mp.insert( { "Jim", 182 } ); i = mp.insert( { "David", 185 } ); i = mp.insert( { "Ian", 183 } ); for (const auto& [key, val] : mp) { std::cout << key << "," << val << " | "; } system("pause"); return 0; } |
Here are a few more examples of how to use Insert in std::map in Modern C++
std::pair can be used inside the insert method as below,
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i = mp.insert( std::pair{ "Yilmaz", 172 } ); |
you can add multiple pairs as below,
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mp.insert( { { "Yilmaz", 172 }, { "Ata", 178 } }); |
you can create a new map by using insert as below too,
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std::map< std::string, int > mp2 = mp.insert( std::begin(mp), std::end(mp) ); |
std:map is a very strong sorted associative container, it uses iterators like begin() and end(), and in addition to insert() it has other modifiers like clear(), erase(), swap(), etc.
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