Use the std::system() function to execute system commands, which need to include header files and pass in C-style string commands, such as std::system("ls-l"), and the return value is -1, which means that the command processor is not available.

Custom allocator can be used to control the memory allocation behavior of C containers. 1. The LoggingAllocator in the example implements memory operation logging by overloading allocate, deallocate, construct and destroy methods; 2. The allocator needs to define value_type and rebind templates to meet the STL container type conversion requirements; 3. The allocator triggers log output during construction and copying, which is convenient for tracking the life cycle; 4. Actual applications include memory pools, shared memory, debugging tools and embedded systems; 5. Since C 17, construct and destroy can be processed by std::allocator_traits by default

Create a project directory structure, including CMakeLists.txt, src/ and include/; 2. Write CMakeLists.txt, specify the CMake version, project name, C standard and add executable files; 3. Use mkdirbuild to enter the directory and run cmake.. and cmake--build. for compilation; 4. Add multiple source files through add_executable, and use target_include_directories to include the header file path; 5. Use find_package to find external libraries and link with target_link_libraries; 6.

C's stack is a container adapter in STL. It follows the principle of back-in-first-out and must include header files; add elements by push, pop removes the top element, and top accesses the top of the stack. Before the operation, check whether it is empty, which is often used in scenarios such as expression evaluation and backtracking.

Theautokeywordletsthecompilerdeducevariabletypesfrominitializers,reducingverbosityandimprovingmaintainability.Itsimplifiescodewithcomplextypeslikeiteratorsandlambdas,supportsreferencesandconstqualifierstoavoidunnecessarycopies,andadaptsautomaticallyw

The answer is to define a class that contains the necessary type alias and operations. First, set value_type, reference, pointer, difference_type and iterator_category, then implement dereference, increment and comparison operations. Finally, provide begin() and end() methods in the container to return the iterator instance, making it compatible with STL algorithms and range for loops.

AstaticvariableinC retainsitsvaluebetweenfunctioncallsandisinitializedonce.2.Insideafunction,itpreservesstateacrosscalls,suchascountingiterations.3.Inaclass,itissharedamongallinstancesandmustbedefinedoutsidetheclasstoavoidlinkingerrors.4.Staticvaria

Use std::ifstream and std::istreambuf_iterator to efficiently read the entire contents of the file to strings, including spaces and line breaks, and is suitable for medium-sized text files.