C++预编译头文件 bits/stdc++.h

有时候会看到别人包含这样的头文件：

#include "bits/stdc++.h"

这个头文件中有很多预先包含的头文件，内容如下：

// C++ includes used for precompiling -*- C++ -*-

// Copyright (C) 2003-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// .

/** @file stdc++.h
 *  This is an implementation file for a precompiled header.
 */

// 17.4.1.2 Headers

// C
#ifndef _GLIBCXX_NO_ASSERT
#include 
#endif
#include 
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#if __cplusplus >= 201103L
#include 
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#include 
#endif

// C++
#include 
#include 
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#if __cplusplus >= 201103L
#include 
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#endif

#if __cplusplus >= 201402L
#include 
#endif

#if __cplusplus >= 201703L
#include 
#include 
#endif

包含这个头文件后，常用的std库的内容也会包含进行。

有几个注意事项：

• 这个头文件是gcc特有的，clang和MSVC都没有
• 如果你在做题，可以包含这个头文件
• 日常不推荐使用