@echo off
Setlocal Enabledelayedexpansion
set n=0
for /f "delims=" %%i in (a.txt) do (
set "ke=%%i"
set ke1=!ke: =!
set m=0
call :1
)
echo %wang%
pause
goto :eof
:1
if not "!ke1:~%m%,1!"=="" set /a m+=1&goto 1
if %m% gtr %n% set n=%m%&set wang=%ke%
goto :eof

@echo off
set num=0
for /f "delims=" %%i in (a.txt) do set "str=%%i"&call,set "str=%%str: =%%"&call :lp "%%i"
call,echo %%_%num%%% %num%個字符
pause>nul&goto :eof
:lp
set "str=%str:~1%"&set /a n+=1
if defined str goto lp
if %n% geq %num% set "num=%n%"&set "_%num%=%~1"
set "n=0"