C++ program to traverse dictionary

Although C does not have a dictionary, it has a dictionary-like structure called map. Each map entry contains two values ​​− key and mapping value −. Each item is indexed using a key value, and mapped values ​​are the values ​​associated with the key. The mapped values ​​may or may not be unique, but the keys are always unique. In this tutorial, we'll take a look at iterators and how they work with maps.

Iterators in C

The iterator object points to an element in a series of elements. Iterators are commonly used with containers such as arrays and vectors, and have specific collections or operations that can be used to point to specific elements within a given range. The iterator points to the memory location of a specific element of the range and can be incremented or decremented to point to different elements present in the range or container. Let's see how iterators work.

grammar

<container_type> :: iterator iterator_name;

Let us give an example -

The Chinese translation of

Example

is:

Example

#include <iostream>
#include <iterator>
#include <vector>

using namespace std;

int main(){
   //we are using a vector to demonstrate the working of an iterator
   vector<int> myVec = { 10, 20, 30, 40, 50 };
     
   // creating an iterator
   vector<int>::iterator it;
     
   // iterating through the elements
   cout << "The elements are: ";
   //the begin and end are used to define the range
   for (it = myVec.begin(); it < myVec.end(); it++)
      cout << *it << " ";
     
   return 0;   
}

Output

The elements are: 10 20 30 40 50

Use iterator to iterate over the map

This is a fairly simple process, the same as iterating over other containers.

grammar

map<datatype, datatype> mmap;
for (auto itr = my.begin(); itr != mmap.end(); ++itr) {
   cout << itr->first << ": " << itr->second << endl;
}

The Chinese translation of

Example

is:

Example

#include <iostream>
#include <map>

using namespace std;

int main() {
   //initialising the map
   map <string, string> mmap = {{"City", "London"}, {"Country", "UK"}, {"Continent", "Europe"}};

   //iterating through the contents
   for (auto itr = mmap.begin(); itr != mmap.end(); ++itr) {
      cout << itr->first << ": " << itr->second << endl;
   }
   return 0;
}

Output

City: London
Continent: Europe
Country: UK

in conclusion

In C, a map is treated as an ordered collection, which means that the components are ordered according to the value of their key attribute. Red-black trees are used to implement maps in memory, and the time complexity of all operations is logarithmic. When traversing the map, we have to use iterators, otherwise there is no other easier way to access all elements in the map.

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