Unordered Map does not contain a hash function for a pair like it has for int, string, etc, So if we want to hash a pair then we have to explicitly provide it with a hash function that can hash a pair. unordered_map can takes upto 5 arguments:
- Key : Type of key values
- Value : Type of value to be stored against the key
- Hash Function : A function which is used to hash the given key. If not provided it uses default hash function.
- Pred : A function which is used so that no two keys can have same hash values
- Alloc : An object used to define the memory model for the map
hash_function can be anything, given that it can hash the given key.
Prerequisite : How to create an unordered_map of user defined class?
Contents of the unordered_map : [1000, 2000] ==> 1 [2005, 3005] ==> 1 [2000, 3000] ==> 0
Exercise Problem : Nikhil is a travelling salesman and today he is visiting houses in a new locality to sell encyclopedias. The new city is in the from of a grid of x*y(1<=x<=10^9, 1<=y<=10^9) and at every intersection there is a house. Now he is not very good with remembering the houses that he has already visited, so whenever he goes into a house he tells you the coordinate of the house. Your job is to remember the coordinate and at the end of the day tell him all the houses that he visited on that day.
Enter the number of houses that he visited today :5
Enter the coordinate of HouseNo. 1 :1000 12985
Enter the coordinate of HouseNo. 2 :12548 25621
Enter the coordinate of HouseNo. 3 :14586 26481
Enter the coordinate of HouseNo. 4 :12 63
Enter the coordinate of HouseNo. 5 :14689 36945
Houses that he visited today:
- How to create an array with key value pairs in PHP?
- Ways to form n/2 pairs such that difference of pairs is minimum
- Strings in C++ and How to Create them?
- Different ways to create an Object in C#
- How to create an array for JSON using PHP?
- How to create a copy of an object in PHP?
- How to create a List with Constructor in C++ STL
- How to create a Collapsed Sidebar?
- How to create a div element in jQuery ?
- How to create Radial Menu in CSS ?
- How to create five equal columns in Bootstrap ?
- 10 Ways to Create a Stream in Java
- Create a Pandas Series from array
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.