eduarc's blog

Useful C++ "library"
By eduarc, 13 years ago, In English

Hi! See this useful C++ include directive.

#include <bits/stdc++.h>

This let you use any C/C++ standard library without adding extra "includes". No more compilation errors because missing libraries :)

And you can make a shorter version of your template. For example, my template.

  #include <bits/stdc++.h>
  #define _ ios_base::sync_with_stdio(0);cin.tie(0);

  using namespace std;

  int main() { _

    return 0;
  }

I tested it with the GNU/C++ compiler.

More information:

Headers — GCC Documentation

Header file definition:

Linux GCC 4.8.0

Windows MinGW 4.6.1

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13 years ago, hide # |
 
Vote: I like it +5 Vote: I do not like it

So how can I wrap up these library? Suppose I have — 

#include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <pair>
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    13 years ago, hide # ^ |
    ← Rev. 2  
    Vote: I like it +19 Vote: I do not like it 
    #include <pair>

    ???

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    12 years ago, hide # ^ |
    ← Rev. 6  
    Vote: I like it +5 Vote: I do not like it

    First: there is no header file called <pair>, std::pair exists in a standard header called <utility> ;Second: you can wrap up all these lines by deleting all of them and writing one line:

    #include <bits/stdc++.h>
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13 years ago, hide # |
 
Vote: I like it +4 Vote: I do not like it

Doesn't work for MS C++ :(

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13 years ago, hide # |
 
Vote: I like it +5 Vote: I do not like it

Is this portable in all the programming sites that support g++?

want to hear from experienced C++ coders like "Venco" in topcoder.

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13 years ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

can you please explain why it works and meaning of the 2 lines #include <bits/stdc++.h> #define _ ios_base::sync_with_stdio(0);cin.tie(0);

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13 years ago, hide # |
 
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I tested it on Linux 12.04 CNU c++ and it works. THAAAAAAAAAAAAAAANKS!!!

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13 years ago, hide # |
 
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Thanks. Today I tested this on UVa Online Judge, it worked !

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13 years ago, hide # |
← Rev. 2  
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You can also use a constructor in a global object to set up iostreams. This way you don't have to add anything in main():

struct _ { ios_base::Init i; _() { cin.sync_with_stdio(0); cin.tie(0); } } _;

int main()
{

}

The ios_base::Init object is there to ensure that cin is constructed prior to its use.

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    13 years ago, hide # ^ |
     
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    Thanks a lot, much clearer. Can you explain how struct _ { ... } _; works?

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      13 years ago, hide # ^ |
       
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      It is idential to struct _ { }; _ _; or struct x { }; x x;. C++ allows a variable to have the same name as a class.

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        13 years ago, hide # ^ |
         
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        I mean why is it executes in the beginning of program?

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          13 years ago, hide # ^ |
          ← Rev. 5  
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          Code above is compressed version of this.

          struct MyStruct {
ios_base::Init i; //i'm not sure but i don't think this line is needed
MyStruct() { cin.sync_with_stdio(0); cin.tie(0); };
};
MyStruct myVariable;

          Now when myVariable is initialized the default constructor is called executing "cin.sync_with_stdio(0) and cin.tie(0)"

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12 years ago, hide # |
 
Vote: I like it -6 Vote: I do not like it

Why does the code not work on ideone?

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11 years ago, hide # |
 
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Why does my console keep on saying "No such file or directory" and "unresolved inclusion"? Thanks for any help.

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11 years ago, hide # |
 
Vote: I like it +7 Vote: I do not like it

Why doesn't tourist use it ?!

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11 years ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

+1

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11 years ago, hide # |
 
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seems doesn't work in clang.....

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    10 years ago, hide # ^ |
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    At least if you are on Mac OSX the solution is simple. You go to folder /Library/Developer/CommandLineTools/usr/include/c++/v1/bits , at least on two Macs I have seen this is the folder, for some others it might be different. And then copy the stdc++.h file from here into this folder. Also it is likely that the bits folder will not exist, so when you go to /Library/Developer/CommandLineTools/usr/include/c++/v1/ you might first have to create bits folder in there. Then when you put #include <bits/stdc++.h> in your program it will include the file you have just added!

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    10 years ago, hide # ^ |
     
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    For Xcode Users on Mac, you can use /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/bits path to add file.

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10 years ago, hide # |
 
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You can see contents of <bits/stdc++.h> here.

As you see, it includes all of the standard library.

But it has not gnu libraries like <ext/pb_ds/assoc_container.hpp>(when you want to use ordered_set)

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10 years ago, hide # |
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Vote: I like it -33 Vote: I do not like it

Actually it isn't portable. The result of using this header file is undefined in C++ Standard. Please don't use it in contests unless you are sure about the compiler. Please visit https://github.com/cplusplus/draft to see if it is actually in the standard.

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6 years ago, hide # |
 
Vote: I like it -12 Vote: I do not like it

Using #include<bits/stdc++.h> has advantages like

  • We only need one line include

  • We dont need to take care about the libraries

But everything has 2 sides, the disadvantages is need to be aware

  • It may not work in some compiler and upgrade compiler may break the program

  • It contain many libraries you dont need, which can make the compiler run longer to access all the functions insides all the libreary.

And there is the fact that <bits/stdc++.h> has warned:

  • This is an implementation file for a precompiled header.
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