YouCompleteMe/third_party/ycmd/third_party/cregex" does not appear to contain CMakeLists.txt.

•  rm -rf YouCompleteMe/third_party/ycmd/third_party/cregex 
•  git submodule update --init --recursive  at the dir of "YouCompleteMe/third_party/ycmd/third_party"

完美解决！

set nocompatible              " be iMproved, required 
filetype off                  " required    

" set the runtime path to include Vundle and initialize
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()
" alternatively, pass a path where Vundle should install plugins
"call vundle#begin('~/some/path/here')

" let Vundle manage Vundle, required
Plugin 'VundleVim/Vundle.vim'

Plugin 'scrooloose/nerdtree'
Plugin 'jistr/vim-nerdtree-tabs'
Plugin 'Xuyuanp/nerdtree-git-plugin'

Plugin 'majutsushi/tagbar'
Plugin 'scrooloose/syntastic'
Plugin 'vim-airline/vim-airline'
Plugin 'vim-airline/vim-airline-themes'
Plugin 'jiangmiao/auto-pairs'
Plugin 'Valloric/YouCompleteMe'


Plugin 'tpope/vim-fugitive'
Plugin 'rstacruz/sparkup', {'rtp': 'vim/'}


" The following are examples of different formats supported.
" Keep Plugin commands between vundle#begin/end.
" plugin on GitHub repo
" Plugin 'tpope/vim-fugitive'
" plugin from http://vim-scripts.org/vim/scripts.html
" Plugin 'L9'
" Git plugin not hosted on GitHub
" Plugin 'git://git.wincent.com/command-t.git'
" git repos on your local machine (i.e. when working on your own plugin)
" Plugin 'file:///home/gmarik/path/to/plugin'
" The sparkup vim script is in a subdirectory of this repo called vim.
" Pass the path to set the runtimepath properly.
" Plugin 'rstacruz/sparkup', {'rtp': 'vim/'}


" Pass the path to set the runtimepath properly.
" Plugin 'rstacruz/sparkup', {'rtp': 'vim/'}
" Avoid a name conflict with L9
" Plugin 'user/L9', {'name': 'newL9'}

" All of your Plugins must be added before the following line
call vundle#end()            " required
filetype plugin indent on    " required
" To ignore plugin indent changes, instead use:
"filetype plugin on
"
" Brief help
" :PluginList       - lists configured plugins
" :PluginInstall    - installs plugins; append `!` to update or just :PluginUpdate
" :PluginSearch foo - searches for foo; append `!` to refresh local cache
" :PluginClean      - confirms removal of unused plugins; append `!` to auto-approve removal
"
" see :h vundle for more details or wiki for FAQ
" Put your non-Plugin stuff after this line

" airline


"设置打开vim的时候默认打开目录树"
let g:nerdtree_tabs_open_on_console_startup=1
" 关闭NERDTree快捷键
map <C-t> :NERDTreeToggle<CR>

""当NERDTree为剩下的唯一窗口时自动关闭
autocmd bufenter * if (winnr("$") == 1 && exists("b:NERDTree") && b:NERDTree.isTabTree()) | q | endif
let g:NERDTreeDirArrowExpandable = '►'
let g:NERDTreeDirArrowCollapsible = '▼'
let NERDTreeAutoCenter=1
" 是否显示隐藏文件
let NERDTreeShowHidden=1
" 设置宽度
let NERDTreeWinSize=23

"let g:NERDTreeIndicatorMapCustom = {
"     "Modified"  : "✹",
"     "Staged"    : "✚",
"     "Untracked" : "✭",
"     "Renamed"   : "➜",
"     "Unmerged"  : "═",
"     "Deleted"   : "✖",
"     "Dirty"     : "✗",
"     "Clean"     : "✔︎",
"     "Ignored"   : "☒'",
"     "Unknown"   : "?"
"     }


"""""""""""""""""""""""""""""""""""""""
let g:airline_powerline_fonts = 1
set t_Co=256
set laststatus=2

" ycm
"let g:ycm_python_binary_path='/usr/bin/python'
let g:ycm_confirm_extra_conf=0

"let g:ycm_server_python_interpreter='/usr/bin/python'
"let g:ycm_global_ycm_extra_conf='~/.vim/.ycm_extra_conf.py'
let g:ycm_global_ycm_extra_conf='~/.vim/bundle/YouCompleteMe/third_party/ycmd/.ycm_extra_conf.py'

let g:ycm_confirm_extra_conf=0
"let g:clang_use_library=1
set completeopt-=preview

" 不显示开启vim时检查ycm_extra_conf文件的信息  
let g:ycm_confirm_extra_conf=0
" 开启基于tag的补全，可以在这之后添加需要的标签路径  
let g:ycm_collect_identifiers_from_tags_files=1
"注释和字符串中的文字也会被收入补全
let g:ycm_collect_identifiers_from_comments_and_strings = 0
"" 输入第2个字符开始补全
let g:ycm_min_num_of_chars_for_completion=2
" 禁止缓存匹配项,每次都重新生成匹配项
let g:ycm_cache_omnifunc=0

" " 开启语义补全
let g:ycm_seed_identifiers_with_syntax=1
" "在注释输入中也能补全
let g:ycm_complete_in_comments = 1
" "在字符串输入中也能补全
let g:ycm_complete_in_strings = 1
" " 设置在下面几种格式的文件上屏蔽ycm

let g:ycm_filetype_blacklist = {
       'tagbar' : 1,
       'nerdtree' : 1,
      }


let g:ycm_key_list_select_completion = ['<Down>']
let g:ycm_key_list_previous_completion = ['<Up>']
" 修改对C函数的补全快捷键，默认是CTRL + space，修改为ALT + ;
let g:ycm_key_invoke_completion = '<M-;>'

"let g:ycm_add_preview_to_completeopt = 0
""let g:ycm_show_diagnostics_ui = 0
let g:ycm_server_log_level = 'info'
let g:ycm_min_num_identifier_candidate_chars = 2
let g:ycm_collect_identifiers_from_comments_and_strings = 1
let g:ycm_key_invoke_completion = '<c-z>'
"set completeopt=menu,menuone

noremap <c-z> <NOP>
let g:ycm_semantic_triggers =  {
                         'c,cpp,python,java,go,erlang,perl': ['re!w{2}'],
                         'cs,lua,javascript': ['re!w{2}'],
                         }


synta on

set number
set cindent
set autoindent

set expandtab

set smarttab
" set mouse=a
set shiftwidth=4
set softtabstop=4
set hls
set bg=dark

 注意：补全c++头文件，或者c的头文件，需要在 .ycm_extra_conf.py 文件里修改 flags

flags = [

] 里面加上，下面

'-isystem',
'/usr/include',
'-isystem',
'/usr/include/c++/5.4.0',