安装了YCM后，VIM自带的补全不能用了，求助

应该是快捷键冲突了,在vimrc里添加

let g:ycm_key_list_select_completion = ['<C-n>', '<Down>']
let g:ycm_key_list_previous_completion = ['<C-p>', '<Up>']
如果你也使用了supertab，加上这句

let g:SuperTabDefaultCompletionType = '<C-n>'
如果你同时使用了supertab+Ultisnips,加上

" better key bindings for UltiSnipsExpandTrigger
let g:UltiSnipsExpandTrigger = "<tab>"
let g:UltiSnipsJumpForwardTrigger = "<tab>"
let g:UltiSnipsJumpBackwardTrigger = "<s-tab>"