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Useful C++ code snippets


Setting up  Precision to given decimal point 
“std:setprecision()”  method used along with  “std:fixed” provides precision of 
outputting floating point numbers correct to decimal numbers mentioned in the parameter 
of the setprecision method.
header file
#include <iomanip>
std:setprecision() defined no of digits in number. Without using std:fixed() method setprecision()  will   limit whole numbers digits to given precision.
In order to print precision of decimal point both setprecision() and fixed() method using before printing values,
code snippet :
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// setprecision example

#include <iostream>     // std::cout, std::fixed
#include <iomanip>      // std::setprecision

int main(){

     double   doubeleValue =3.34535 ;

     std::cout <<  std::setprecision(4) ;
     std::cout <<  doubeleValue<< '\n';
      // Output : 3.345  -without fixed


      std::cout << std::fixed;
      std::cout <<  doubeleValue<< '\n';// Output : 3.3453

     std::cout <<  std::setprecision(2) <<std::fixed<< doubeleValue<< '\n';
      // Output : 3.34

    return 0;
} 



Getting input from Terminal / CommandLine


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// setprecision example

#include <iostream>
#include <string>

using namespace std;

int main(){

    int getInt;
    std::cout << "Get Int : " ;

    cin >> getInt  ;
    std::cout << "int " << getInt<<'\n';
    // using cin >> you can get any primative data type

    /*  to get whole line as string use string and getline method
    */
    string str;
    std::cout << "String :" ;
    std::getline(std::cin,str);
    std::cout << str << '\n';

    return 0;
}


Getting multiple numeric values in same Line of Terminal/CMD
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#include <iostream>
#include <sstream>
#include <iterator>
#include <string>
#include <vector>

int main() 
{
    std::string s;

    std::getline( std::cin, s );

    std::istringstream is( s );

    std::vector<int> v( ( std::istream_iterator<int>( is ) ), std::istream_iterator<int>() );

    for ( int x : v) std::cout << x << ' ';
    std::cout << std::endl;

    return 0;
}

Getting the power of value
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/* pow example */
#include <stdio.h>      /* printf */
#include <math.h>       /* pow */

int main ()
{
  printf ("7 ^ 3 = %f\n", pow (7.0, 3.0) );
  printf ("4.73 ^ 12 = %f\n", pow (4.73, 12.0) );
  printf ("32.01 ^ 1.54 = %f\n", pow (32.01, 1.54) );
  return 0;
}

Reading a text file
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// ios::exceptions
#include <iostream>
#include <fstream>
using namespace std;

void do_something_with(char ch) {} // Process the character 

int main () {
  ifstream file;
  file.exceptions ( ifstream::badbit ); // No need to check failbit
  try {
    file.open ("test.txt");
    char ch;
    while (file.get(ch)) do_something_with(ch);
    // for line-oriented input use file.getline(s)
  }
  catch (const ifstream::failure& e) {
    cout << "Exception opening/reading file";
  }

  file.close();

  return 0;
}

Writing a text file
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// writing on a text file
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile ("example.txt");
  if (myfile.is_open())
  {
    myfile << "This is a line.\n";
    myfile << "This is another line.\n";
    myfile.close();
  }
  else cout << "Unable to open file";
  return 0;
}

Calculating the run time of given code
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// writing on a text file
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile ("example.txt");
  if (myfile.is_open())
  {
    myfile << "This is a line.\n";
    myfile << "This is another line.\n";
    myfile.close();
  }
  else cout << "Unable to open file";
  return 0;
}



 
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