Map of Maps in C++
To create a std::map of maps first, we need to declare a map where the key is of the desired type and the value is of the type map. We can do that by passing the value template parameter as a map.
Syntax to Declare Map of Maps
map < keytype, map <innerKeyType, valueType> > myMap
C++ Program to Create a Map of Maps
The below program demonstrates how we can create a map of maps in C++ STL.
C++
// C++ program to illustrate how to create a map of maps #include <iostream> #include <map> using namespace std; int main() { // Creating a map of maps map< int , map< int , string> > myMap; // Adding key-value pairs to the map of maps myMap[1][1] = "one" ; myMap[1][2] = "two" ; myMap[2][1] = "two" ; myMap[2][2] = "four" ; // Printing the map of maps cout << "Map of maps:" << endl; for ( const auto & pair1 : myMap) { for ( const auto & pair2 : pair1.second) { cout << pair1.first << ", " << pair2.first << " => " << pair2.second << endl; } } return 0; } |
Map of maps: 1, 1 => one 1, 2 => two 2, 1 => two 2, 2 => four
Time Complexity: O(N * M log(N*M) ), here N is the number of maps in the map and M is the average size of the inner maps
Auxiliary Space: O(N * M)
How to Create a Map of Maps in C++?
In C++, maps are associative containers provided by the STL library of C++, that allow the users to store data in key-value pairs where the keys must be unique. In this article, we will learn how to create a map of maps in C++.
For Example,
Input: myMap1={1, "C++"}; myMap2={1, "Java"}; myMap3={2, "Python"}; Output: Map Elements: { {1: {1, "C++"} }, {2: {1, "Java"} }, {3: {2, "Python"} }