C++ Tutorial Index

C++ Tutorial C++ History C++ Installation C++ First Program C++ cin and cout C++ Data type C++ Variable C++ operator C++ Keywords

C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file


C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Constructor Overloading in C++ Different Ways to Compare Strings in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++

Maps in C++


Maps in C++ are the containers associated with key and mapped values. By keys and mapped values, we mean that the maps are used to store elements formed by the combination of the keys and mapped values.

In other words, maps are functions found in the Standard Template Library (STL) that store key-value pairs that are unique. It can also be inserted or deleted but the value cannot be altered although values associated with the keys can be modified.

Let's look at maps to see how they are created.

typedef pair<const Key, T> value_type;


     Key is the type of key and value is the type of value that needs to be assigned.

Note: The keys and values are always inserted as pairs. We simply cannot just enter a key or a value individually.

Syntax of map function:

     class Key,
     class T,
     class Compare = std::less<Key>,
     class Allocator = std::allocator<std::pair<const Key, T> >
 > class map; 

The above member functions can be grouped with the following definitions.

Member FunctionsDefinitions
key_type    Key
mapped_type    Map
value_typePair<const Key, T>
size_typeUnsigned integer(std::size_T)
key_compareFor comparing
pointerConst pointer
const iteratorConst<iterator>
const reverse_iteratorReverse_iterator<const_iterator>

Let us now look at the programming examples for maps.

Example 1:

 using namespace std;
 int main ()
   map<char,int> first;
    map<char, int>::iterator i;
    for(i=first.begin(); i!=first.end(); ++i){
       cout << it->first << " => " << it->second << '\n';
   return 0;


Maps in C++


In the above code depiction, we initialized the map function with the members of type character and integer since we are assigning character values with an integer. The function map consists of an iterator I, which iterates from start to end using the functions associated with begin() and end(). It later increments the value by 1. The output is is printed on the console.

Example 2:

 int main()
     std::map<std::string, int> planets;
     planets.insert(std::make_pair("Jupiter", 6));
     planets.insert(std::make_pair("Titan", 7));
     planets["Sun"] = 0;
     planets["Saturn"] = 5;
     std::map<std::string, int>::iterator it = planets.begin();
     while(it != planets.end())
         std::cout<<it->first<<" :: "<<it->second<<std::endl;
     if(planets.insert(std::make_pair("Saturn", 5)).second == false)
         std::cout<<"Element with key 'Saturn' already exists"<<std::endl;
     if(planets.find("Sun") != planets.end())
         std::cout<<"word 'Sun' found"<<std::endl;
     if(planets.find("Pluto") == planets.end())
         std::cout<<"word 'Pluto' not present"<<std::endl;
     return 0;


Maps in C++


The above code is implemented just to showcase how maps work with strings. Here, we assigned our map function having arguments in the form of strings and also have key values of integers. Since we have already come across the fact that maps accept mapped values and keys in pairs, therefore each code is assigned to some values respective of their definition in the map function.

The function returns the values assigned with the respective functions that have their values already assigned. It returns false if they already exist or not present within the pair of occurrences.

Additional functions associated with Maps in STL

  1. begin() : Return first element to the iterator in maps.
  • end(): Return last element to the iterator in maps.
  • size(): gives the size of the elements present.
  • empty(): checks whether map is empty.
  • pair insert(key_value,map_value): used for adding value.
  • erase(): removes the elements which the iterators points.
  • clear(): cleans or removes all the elements from the maps.
  • operator[]: returns element with the key given.
  • at: retrieves the given element associated with key.
  1. cbegin(): returns constant iterator pointing first element.
  1. cend(): return constant iterator point last element.
  2. crbegin(): return constant reverse iterator pointing first element.
  3. crend(): return constant reverse iterator pointing last element.
  4. rbegin(): return reverse iterator pointing first element.
  5. rend(): return reverse iterator pointing last element.

Advantages of using Maps in C++

The advantages of using Maps in C++ are:

  • Lookup time
  • Well ordered
  • Insertion

Let’s discuss the above advantages in detail.

Lookup time:

If keys are known to fall in a narrow integer range, then an array (or preferably a vector) is ideal but using maps reduces the effort of fetching time to 0(1) complexity. A map lets you maintain reasonable lookup performance (O(log(n))). But only takes up 2 spots to store the memory.  A map allow us to maintain lookup in O(log(n)) complexity and also allow us to use any type of operator through arguments using templates. Also, it allows us to compare different keys. Thus, to lookup on maps of strings will let us map the values like -


Well ordered:

Keys in maps are stored in proper order allowing us to iterate over all the items from beginning to end, in sorted key order. Although it can be done using dynamic arrays called vectors, but maps allow having arbitrary key types without defined ordering.


Inserting any element in array/vector requires shifting all the elements to the left. In the case of dynamic arrays, we may need to resize the vector which consumes the entire memory for the array. Therefore, the time complexity is increased. A map has reasonable insertion time (O(log(n))).