@echo off
set str=bBAathToHOMmEe

for %%A in (#A,#B,#C,#D,#E,#F,#G,#H,#I,#J,#K,#L,#M,#N,#O,#P,#Q,#R,#S,#T,#U,#V,#W,#X,#Y,#Z) do (
	set %%A=%%A
)
setlocal enabledelayedexpansion
:cut
	set letter=!str:~0,1!
	for %%a in (!letter!) do (
		if "#%%a"=="!#%%a!" (
			set uprstr=!uprstr!%%a
		) else (
			set lowstr=!lowstr!%%a
		)
	)
	set str=!str:~1!
	if "!str!"=="" (set/p=%lowstr%%uprstr%&exit)
	goto :cut
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my $lower = my $upper = 'bBAathToHOMmEe';
$lower =~s/[A-Z]//g;
$upper =~s/[a-z]//g;
print $lower.$upper;
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如果不用正则，也就是遍历，加点糖

my @s = split('', 'aDbEcFghijkLMN');
my $n = 0;
grep { print $_ if ( $_ ~~ ['a'..'z'] ) } @s;
grep { print $_ if ( $_ ~~ ['A'..'Z'] ) } @s;
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u = ''
l = ''

for c in 'bBAathToHOMmEe':
    if c in "abcdefghijklmnopqrstuvwxyz":
        l+=c
    else:
        u+=c

print(l+u)
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@echo off
powershell ^
    $a='bBAathToHOMmEe'.ToCharArray()^|group {1*$_ -lt 97};^
    -join ($a[0].group+$a[1].group);
pause
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@echo off
cd /d %tmp%&cmd /u /c echo;bBAathToHOMmEe|more>$
(for /f %%a in ('findstr [abcdefghijklmnopqrstuvwxyz] $^&findstr [ABCDEFGHIJKLMNOPQRSTUVWXYZ] $') do set /p=%%a)<nul
pause
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str = "bBAathToHOMmEe";
console.log(str.replace(/[A-Z]/g, '') + str.replace(/[a-z]/g, ''));
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@echo off & setlocal enableDelayedExpansion
set "str=bBAathToHOMmEe"
for /L %%i in (0 1 8000) do (
    set "c=!str:~%%i,1!"
    if "!c!" neq "" (
        (for /f "delims=ABCDEFGHIJKLMNOPQRSTUVWXYZ" %%c in ("!c!") do ( set "rl=!rl!!c!" )) || (set "RU=!RU!!c!")
    ) else echo;!rl!!RU! & pause & exit
)
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'&@(Cls&Cscript -nologo -e:vbscript "%~0"&Pause&Exit)

str="bBAathToHOMmEe"

For Cut = 1 To Len(str)
	If LCase(Mid(str,cut,1)) = Mid(str,cut,1) Then
		NewLstr=NewLstr & Mid(str,cut,1)
	ElseIf UCase(Mid(str,cut,1)) = Mid(str,cut,1) Then
		NewUstr=NewUstr & Mid(str,cut,1)
	End If
Next

WScript.Echo str & " -- > " & NewLstr & NewUstr
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@echo off & setlocal enabledelayedexpansion
set str=BaAbTcHdOeMfEg
set dupl=%str%
set "uc="
set "lc="
for %%a in (a b c d e f g h i j k l m n o p q r s t u v w x y z) do (
    set dupl=!dupl:%%a=%%a!
)

set /a n = 0
:lp
    if "!str:~%n%, 1!" == "!dupl:~%n%, 1!" (
        set lc=!lc!!str:~%n%, 1!
    ) else (
        set uc=!uc!!str:~%n%, 1!
    )
    set /a n+=1
if not "!str:~%n%!" == "" goto :lp

echo %lc%%uc%
pause
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@echo off&setlocal enabledelayedexpansion
set s=bBAathToHOMmEe
for /f "delims=" %%a in ('tree "\*\%s%"^|find ":\*\"') do set "t=%%~nxa"
rem 或者dir /L
set n=0
:lp
if "!s:~%n%,1!" neq "!t:~%n%,1!" (
    set /p=!s:~%n%,1!<nul
) else (
    set r=!r!!s:~%n%,1!
)
set /a n+=1
if "!s:~%n%!" neq "" goto :lp
echo;%r%
pause
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@echo off&setlocal enabledelayedexpansion
set str=bBAathToHOMmEe
set str_bp=%str%
for %%a in (A B C D E F G H I J K L M N O P Q R S T U V W X Y Z) do call set str_bp=%%str_bp:%%a=%%a%%
for /l %%a in (0 1 14) do (
	for /f "tokens=1,2 delims=#" %%b in ('call echo;%%str:~%%a^,1%%#%%str_bp:~%%a^,1%%') do (
		if not "%%b"=="%%c" (set lc=!lc!%%b) else ( set uc=!uc!%%c)
))
echo;!lc!!uc!
pause
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@echo off&setlocal enabledelayedexpansion
set str=bBAathToHOMmEe
set str_bp=%str%
for %%a in (A B C D E F G H I J K L M N O P Q R S T U V W X Y Z) do set str_bp=!str_bp:%%a=%%a!
for /l %%a in (0 1 14) do (
	for /f "tokens=1,2 delims=#" %%b in ('echo;!str:~%%a^,1!#!str_bp:~%%a^,1!') do (
		if not "%%b"=="%%c" (set lc=!lc!%%b) else ( set uc=!uc!%%c)
))
echo;!lc!!uc!
pause
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@echo off&setlocal enabledelayedexpansion
set str=bBAathToHOMmEe
set str_bp=%str%
for %%a in (A B C D E F G H I J K L M N O P Q R S T U V W X Y Z) do set str_bp=!str_bp:%%a=%%a!
for /l %%a in (0 1 14) do (
    if not "!str:~%%a,1!"=="!str_bp:~%%a,1!" (set lc=!lc!!str:~%%a,1!) else ( set uc=!uc!!str_bp:~%%a,1!)
)
echo;!lc!!uc!
pause
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In [89]: bat = "bBAathToHOMmEe"

In [90]: ''.join(re.findall("[a-z]",bat) + re.findall("[A-Z]",bat))
Out[90]: 'bathomeBATHOME'
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for /l %%a in (0 1 14) do (
    if not "!str:~%%a,1!"=="!str_bp:~%%a,1!" (set lc=!lc!!str:~%%a,1!) else ( set uc=!uc!!str_bp:~%%a,1!)
)
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$s = "cDbEFa";
while ( $s =~s/([A-Z])([a-z])/$2$1/) {}
print $s
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::*****************************************************************************
  @ECHO OFF&MODE CON COLS=100 LINES=30&CLGO "%~F0"&PAUSE>NUL&EXIT /B
::*****************************************************************************

/*
  谢尔宾斯基地毯，酷码；
*/

//入口函数
TO MAIN
	FOR :A 1 6
		CS
		WAIT 10
		MAKE :PENX=-330 :PENY=220 
		TEXT 22 3 8 微软雅黑 Sierpinski-Level:{:A}
		MAKE :PENX=-200 :PENY=-200 :PENC=6 :PENW=10 :PENS=0
		XEBD 380 :A
		WAIT 500	
	]

//谢尔宾斯基主循环
TO XEBD :L :N
	REPEAT 4
		FD :L
		RT 90
	]

	XK :L
	XEB :L/3 :N-1

//地毯分循环
TO XEB :L :N
	IF :N=0 
		STOP
	]

	XK :L
	XEB :L/3 :N-1

	REPEAT 2
		PU
		FD :L
		PD
		XK :L
		XEB :L/3 :N-1
	]

	REPEAT 2
		PU
		RT 90
		FD :L
		LT 90
		PD
		XK :L
		XEB :L/3 :N-1
	]

	REPEAT 2
		PU
		BK :L
		PD
		XK :L
		XEB :L/3 :N-1
	]

	PU
	LT 90
	FD :L
	RT 90
	PD
	XK :L
	XEB :L/3 :N-1

	PU
	LT 90
	FD :L
	RT 90
	PD

//细节补枝
TO XK :L
	PU
	FD :L/3
	RT 90
	FD :L/3
	LT 90
	PD

	REPEAT 4
		FD :L/3
		RT 90
	]

	MAKE :PENC=RAND(15)+1
	PU
	BK :L/3
	LT 90
	FD :L/3
	RT 90
	PD
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::*****************************************************************************
  @ECHO OFF&MODE CON COLS=100 LINES=30&CLGO "%~F0"&PAUSE>NUL&EXIT /B
::*****************************************************************************

//入口函数
TO MAIN
	FOR :A 2 12
		CS
		WAIT 10
		MAKE :PENX=-330 :PENY=220 
		TEXT 22 3 8 微软雅黑 Sierpinski-Level:{:A}
		MAKE :PENX=0 :PENY=-200 :PENC=6 :PENW=2 :PENS=2	
		TREE 100 :A 20 0.75
		WAIT 50	
	]



TO TREE :L :N :ANGEL :RATE
	IF :N=0
		STOP
	]
	FD :L 
	RT :ANGEL
	TREE :L*:RATE :N-1 :ANGEL :RATE
	LT :ANGEL*2
	TREE :L*:RATE :N-1 :ANGEL :RATE
	RT :ANGEL 
	BK :L
	MAKE :PENC=RAND(15)+1
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echo bBAathToHOMmEe | sed -r ":a;s/([a-z])([A-Z])/\2\1/;ta"
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@echo off & setlocal enabledelayedexpansion
%1 echo bBAathToHOMmEe | %1 cmd /c %0 : & exit /b

set "list=#ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

for /l %%a in () do (
  choice /c %list:~1% /cs >nul 2>nul

  for %%e in (!errorlevel!) do (
    if %%e leq 26 (
      set uppercase=!uppercase!!list:~%%e,1!
    ) else if %%e leq 52 (
      set lowercase=!lowercase!!list:~%%e,1!
    ) else (
      echo !lowercase!!uppercase!
      pause
      exit /b
    )
  )
)
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@for %%a in (a-z A-Z) do @echo aAbBdD | grep -o [%%a] | gawk "ORS=s;1"
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;Code By 老刘
;编译环境：MASM32 SDK
;编译指令：ml /coff 字母按大小写归并.ASM /link /subsystem:console
;调用方法：CMD传参，参数1为要处理的字符串。
;其他：非大小写字母的字符将被丢弃；传入字符串长度最长为126字符。

Include Masm32rt.INC
.Data?
	Arg db 128 dup (?)
	UpperCaseString db 128 dup (?)
	LowerCaseString db 128 dup (?)
	NewString db 128 dup (?)
.Code
Start:
	Invoke ArgClC,1,Offset Arg
	.If Eax == 1
		Mov Esi,Offset Arg
		Mov Ecx,Offset LowerCaseString
		Mov Edx,Offset UpperCaseString
		
		.While Al != 0	;分割为两个字符串
			LodSB
			.If Al >= 41h && Al <= 5Ah
				Mov Byte Ptr [Edx],Al
				Inc Edx
			.ElseIf Al >= 61h && Al <= 7Ah
				Mov Byte Ptr [Ecx],Al
				Inc Ecx
			.EndIf
		.EndW
		
		;合并到同一个字符串中。
		Mov Edi,Offset NewString
		
		;处理小写字符串
		Sub Ecx,Offset LowerCaseString
		Mov Esi,Offset LowerCaseString
		Rep MovSB
		
		;处理大写字符串
		Sub Edx,Offset UpperCaseString
		Mov Ecx,Edx
		Mov Esi,Offset UpperCaseString
		Rep MovSB
		
		;字符串结尾
		Mov Al,0Ah
		StoSB
		Xor EAX,EAX
		StoSB
		
		;回显字符串
		Invoke StdOut,Offset NewString
	.EndIf
	Invoke ExitProcess,NULL
End Start
End
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@echo off
set "str=bBAathToHOMmEe"
echo;%str%>%temp%\$
sed "s/[A-Z]//g" %temp%\$
sed "s/[a-z]//g" %temp%\$
del %temp%\$
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@echo off
set "str=bBAathToHOMmEe"

:lp
set "ch=%str:~,1%"
for %%a in (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,e,s,t,u,v,w,x,y,z) do (
	if "%%a"=="%ch%" (set "LowerCASE=%LowerCASE%%%a") 
)
for %%a in (A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z) do (
	if "%%a"=="%ch%" (set "UperCASE=%UperCASE%%%a") 
)
set "str=%str:~1%"
if "%str%" neq "" goto :lp
echo;%LowerCASE%%UperCASE%
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#!perl
my $test = 'bBAathToHOMmEe';
print sort { ( $b cmp '^' ) <=> ( $a cmp '^' ) } split '', $test;
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# include <stdio.h>
# include <stdlib.h>
# include <string.h>

char* classify (char*);

int main (){
    char *test = "bBAathToHOMmEe";
    char *clas = classify(test);

    puts(clas);

}

# define new(T, N) malloc ((N) *sizeof(T))
char* classify(char *test){
    int len   = strlen (test);
    char *ret = new(char, len + 1);
    ret[len]  = 0;
    int i = 0, j = len - 1;

    for (char *a = test, *b = test + j; i <= j; a++, b--) {
        if (*a >= 'a') ret[i++] = *a;
        if (*b <  'a') ret[j--] = *b;
    }
    return ret;
}
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