This post will discuss how to print out all keys and values from a std::map or std::unordered_map in C++.

The Point Cloud Library has a good C implementation - If you are up to this task at all, you should be able to both locate it, and translate it into c. If not - you'll have to pay somebody to do it, it's not an entirely trivial task. We recommend reading this tutorial, in the sequence listed in the left menu. C is an object oriented language and some concepts may be new. Take breaks when needed, and go over the examples as many times as needed.

Maps are associative containers whose elements are key-value pairs. Using a map, we can associate a value with some key and later retrieve that value using the same key. The retrieval operation in a map is very fast. There are several ways in C++ to print out all pairs present on the map:

1. Using range-based for-loop

The recommended approach in C++11 is to use the new range-based for-loops for printing the map pairs, as shown below:

Output:

{3: C}
{1: A}
{2: B}

2. Using std::for_each function

Another simple solution is to use std::for_each. It takes an iterator to the beginning and end of the map, and applies a specified function on every pair within that range. The specified function may be a unary function, a lambda expression, or an object of a class overloading the () operator.

Output:

{3: C}
{1: A}
{2: B}

3. Using Iterator

We can also use iterators to iterate a map and print its pairs. It is recommended to use the const_iterator from C++11, as we’re not modifying the map pairs inside the for-loop.

Output:

{3: C}
{1: A}
{2: B}

4. Operator<< Overloading

To get std::cout to accept the map object, we can overload the << operator to recognize an ostream object on the left and a map object on the right, as shown below:

Output:

{3: C}
{1: A}
{2: B}

C Program To Print World Map Online

That’s all about printing out all keys and values from a map in C++.

• Write a Program in c to print Hello World string on screen

Printing 'Hello World' program is one of the simplest programs in C programming languages. It become the traditional first program that many people write while learning a new programming language. Hello world program helps in understanding basic syntax of C programming language and C program structure to novice programmers.

• First line is program is a comment placed between /* and */. Comments are used in a C program to write an explanation or for documentation purpose. When a program becomes very complex, we need to write comments to mark different parts in the program. These comments will be ignored by the compiler at compilation time.


• The next line #include is a preprocessor directive to load the stdio.h(Standard Input/Output header file) library. This library provides some macros and functions for input or output which we can use in our program(like printf and scanf). We need stdio for printing 'Hello World' using printf function.


• The next line is int main(){.The int is what is called the return value. Every C program must have a main() function, and every C program can only have one main() function where program execution begins. The two curly brackets {} are used to group all statements together.


• The next line is printf('Hello World') which is used for printing 'Hello World' string on the screen.


• The next line is return 0. int main() declares that main must return an integer. Returning 0 means we are saying to Operating System that program successfully completed, whereas returning 1 says error while running program.

C Program to print Hello World multiple times using loop

For loops are used to repeat a sequence of statements multiple times till a condition is satisfied(here condition is 'counter < 10'). We initialize counter variable with 0 and increment it after every iteration till it's value is less than 10.

C Program To Print World Map Without

C Program to print Hello World using a function

Don't worry if you didn't understand above code as you may not be familiar with functions yet.

• A comment starts with /*, and ends with */.
• Some header files must be included at the beginning of your C program.
• Every C program should have only one main() function where program execution starts.
• Every statement must end with a semicolon.
• Main returns an integer to Operating system informing about it's termination state. Whether program executed successfully or an error has occurred.

C Program To Print World Map Pdf

C Program To Print World Map