How to Create a Map of Maps in C++ - Step by Step Examples

How to Create a Map of Maps in C++ ?

Answer

To create a map of maps in C++, you can use the standard library's std::map data structure. A map of maps allows you to organize data hierarchically, where each key in the outer map points to another map.

✐ Examples

1 Creating a Map of Maps with Integer Keys and Values

We can create a map of maps in C++ by using the std::map data structure. This example demonstrates creating a map where both the outer and inner maps use integers for keys and values.

For example,

We start by including the necessary headers: #include <iostream> and #include <map>.
We declare a map named outerMap where each value is another map.
We populate the inner maps with key-value pairs.
We insert the inner maps into the outer map using appropriate keys.
We print the resulting map of maps to the console to verify the structure.

C++ Program

#include <iostream>
#include <map>

int main() {
    // Declare a map of maps
    std::map<int, std::map<int, int>> outerMap;

    // Populate the inner maps
    std::map<int, int> innerMap1 = {{1, 10}, {2, 20}, {3, 30}};
    std::map<int, int> innerMap2 = {{4, 40}, {5, 50}, {6, 60}};

    // Insert the inner maps into the outer map
    outerMap[1] = innerMap1;
    outerMap[2] = innerMap2;

    // Print the resulting map of maps
    std::cout << "Map of maps with integer keys and values:" << std::endl;
    for (const auto& outerPair : outerMap) {
        std::cout << "Outer key: " << outerPair.first << std::endl;
        for (const auto& innerPair : outerPair.second) {
            std::cout << "  Inner key: " << innerPair.first << ", value: " << innerPair.second << std::endl;
        }
    }

    return 0;
}

Output

Map of maps with integer keys and values:
Outer key: 1
  Inner key: 1, value: 10
  Inner key: 2, value: 20
  Inner key: 3, value: 30
Outer key: 2
  Inner key: 4, value: 40
  Inner key: 5, value: 50
  Inner key: 6, value: 60

2 Creating a Map of Maps with Mixed Key and Value Types

We can create a map of maps in C++ by using the std::map data structure. This example demonstrates creating a map where the outer map uses strings for keys and the inner maps use integers for keys and strings for values.

For example,

We start by including the necessary headers: #include <iostream> and #include <map>.
We declare a map named outerMap where each value is another map with mixed key and value types.
We populate the inner maps with key-value pairs.
We insert the inner maps into the outer map using appropriate keys.
We print the resulting map of maps to the console to verify the structure.

C++ Program

#include <iostream>
#include <map>
#include <string>

int main() {
    // Declare a map of maps
    std::map<std::string, std::map<int, std::string>> outerMap;

    // Populate the inner maps
    std::map<int, std::string> innerMap1 = {{1, "one"}, {2, "two"}, {3, "three"}};
    std::map<int, std::string> innerMap2 = {{4, "four"}, {5, "five"}, {6, "six"}};

    // Insert the inner maps into the outer map
    outerMap["first"] = innerMap1;
    outerMap["second"] = innerMap2;

    // Print the resulting map of maps
    std::cout << "Map of maps with mixed key and value types:" << std::endl;
    for (const auto& outerPair : outerMap) {
        std::cout << "Outer key: " << outerPair.first << std::endl;
        for (const auto& innerPair : outerPair.second) {
            std::cout << "  Inner key: " << innerPair.first << ", value: " << innerPair.second << std::endl;
        }
    }

    return 0;
}

Output

Map of maps with mixed key and value types:
Outer key: first
  Inner key: 1, value: one
  Inner key: 2, value: two
  Inner key: 3, value: three
Outer key: second
  Inner key: 4, value: four
  Inner key: 5, value: five
  Inner key: 6, value: six

3 Creating a Map of Maps with String Keys and Double Values

We can create a map of maps in C++ by using the std::map data structure. This example demonstrates creating a map where both the outer and inner maps use strings for keys and doubles for values.

For example,

We start by including the necessary headers: #include <iostream> and #include <map>.
We declare a map named outerMap where each value is another map with strings for keys and doubles for values.
We populate the inner maps with key-value pairs.
We insert the inner maps into the outer map using appropriate keys.
We print the resulting map of maps to the console to verify the structure.

C++ Program

#include <iostream>
#include <map>
#include <string>

int main() {
    // Declare a map of maps
    std::map<std::string, std::map<std::string, double>> outerMap;

    // Populate the inner maps
    std::map<std::string, double> innerMap1 = {{"A", 1.1}, {"B", 2.2}, {"C", 3.3}};
    std::map<std::string, double> innerMap2 = {{"D", 4.4}, {"E", 5.5}, {"F", 6.6}};

    // Insert the inner maps into the outer map
    outerMap["group1"] = innerMap1;
    outerMap["group2"] = innerMap2;

    // Print the resulting map of maps
    std::cout << "Map of maps with string keys and double values:" << std::endl;
    for (const auto& outerPair : outerMap) {
        std::cout << "Outer key: " << outerPair.first << std::endl;
        for (const auto& innerPair : outerPair.second) {
            std::cout << "  Inner key: " << innerPair.first << ", value: " << innerPair.second << std::endl;
        }
    }

    return 0;
}

Output

Map of maps with string keys and double values:
Outer key: group1
  Inner key: A, value: 1.1
  Inner key: B, value: 2.2
  Inner key: C, value: 3.3
Outer key: group2
  Inner key: D, value: 4.4
  Inner key: E, value: 5.5
  Inner key: F, value: 6.6

Summary

In this tutorial, we learned How to Create a Map of Maps in C++ language with well detailed examples.

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How to Create a Map of Maps in C++ - Step by Step Examples