Maps are associative containers that store elements in a mapped fashion. Each element has a key value and a mapped value. No two mapped values can have same key values.
This operator is used to reference the element present at position given inside the operator. It is similar to the at() function, the only difference is that the at() function throws an out-of-range exception when the position is not in the bounds of the size of map, while this operator causes undefined behaviour.
mapname[key] Parameters : Key value mapped to the element to be fetched. Returns : Direct reference to the element at the given key value.
Input : map mymap; mymap['a'] = 1; mymap['a']; Output : 1 Input : map mymap; mymap["abcd"] = 7; mymap["abcd"]; Output : 7
Errors and Exceptions
1. If the key is not present in the map, it shows undefined behaviour.
2. It has a no exception throw guarantee otherwise.
Time Complexity: O(logn)
- Implementing upper_bound() and lower_bound() for Ordered Set in C++
- How to flatten a Vector of Vectors or 2D Vector in C++
- Queue of Pairs in C++ STL with Examples
- Remove odd frequency characters from the string
- Count of multiples in an Array before every element
- Minimum distance between any two equal elements in an Array
- Different ways to use Const with Reference to a Pointer in C++
- std::to_address in C++ with Examples
- Program to create Custom Vector Class in C++
- std::is_trivially_copy_constructible in C/C++
- Difference between Python and C++
- tgamma() method in C/C++ with Examples
- boost::type_traits::is_array Template in C++
- boost is_pointer template in C++
- Stack of Pair in C++ STL with Examples
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.