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Just give a group of strings, such as a b c
List all permutations of a b c, that is, the output is as follows

a b c
a c b
b a c
b c a
c a b
c b a

I use the brute-force method, triple for loops can get such results, but the number of characters is not necessarily...
Like this... Ask the expert... Hope to summarize an efficient and practical method...

Last edited by pusofalse on 2008-12-28 at 03:32 ]

@echo off&setlocal enabledelayedexpansion

del ts.txt>nul 2>nul

set var=1 2 3

:1

if defined var5 set var=%var5%

for %%a in (%var%) do (

	set dx=%%a

	set/a mn+=1

	set !mn!=%%a

	call :lp

)



if defined had echo 完成&pause>nul&exit/b

for /l %%a in (%mn% -1 1) do set "var5=!var5!!%%a! "

set had=had

goto 1





:lp

set var1=!var:%dx%=!

for %%a in (%var1%) do (

	set "var3=!var3!%%a "

)

>>ts.txt echo %var3%%dx%

set "%var3%%dx%=abcd"

set var3=

Worked on it for a whole morning, and then found out there's a major BUG. It turns out that only when there are three characters can all combinations be arranged. If there are more or fewer, it goes wrong. It has to be 3. I'm asking all the experts, is there a good way?

@echo off&setlocal enabledelayedexpansion

del ts.txt>nul 2>nul

set var=1 2 3

:1

if defined var5 set var=%var5%

for %%a in (%var%) do (

	set dx=%%a

	set/a mn+=1

	set !mn!=%%a

	call :lp

)



if defined had echo 完成&pause>nul&exit/b

for /l %%a in (%mn% -1 1) do set "var5=!var5!!%%a! "

set had=had

goto 1





:lp

set var1=!var:%dx%=!

for %%a in (%var1%) do (

	set "var3=!var3!%%a "

)

>>ts.txt echo %var3%%dx%

set "%var3%%dx%=abcd"

set var3=

Last edited by pusofalse on 2008-6-29 at 10:29 AM ]

@echo off&setlocal enabledelayedexpansion

if exist temp.txt del /q temp.txt

:begin

set code=abcd&set str=&set n=4

:again

set /a a=%random%%%%n%

set a=!code:~%a%,1!

set code=!code:%a%=!

set str=%str%%a%

set /a n-=1

if "%str:~3%" equ "" goto again

if defined var for %%i in (%var%) do if "%%i" equ "%str%" goto begin

echo %str%>>temp.txt

set var=%var% %str%

set /a m+=1

if %m% lss 24 goto begin

sort temp.txt&del /q temp.txt

pause>nul

I don't know if this meets the requirements:

@echo off&setlocal enabledelayedexpansion

if exist temp.txt del /q temp.txt

:begin

set code=abcd&set str=&set n=4

:again

set /a a=%random%%%%n%

set a=!code:~%a%,1!

set code=!code:%a%=!

set str=%str%%a%

set /a n-=1

if "%str:~3%" equ "" goto again

if defined var for %%i in (%var%) do if "%%i" equ "%str%" goto begin

echo %str%>>temp.txt

set var=%var% %str%

set /a m+=1

if %m% lss 24 goto begin

sort temp.txt&del /q temp.txt

pause>nul

The code given by Senior ZW also has bugs... It can only arrange combinations of four characters. If there are more than a few, only the first four are retained... If there are fewer, an error of dividing by zero will occur... The randomly given string, the number of strings is unknown...

@echo off&setlocal enabledelayedexpansion

if exist temp.txt del /q temp.txt

:enter

cls&set /p codes=请输入字符组(字符间请用空格格开)：

if not defined codes goto enter

for %%i in (%codes%) do set /a m+=1

set /a num=1,x=m,y=m-1

:lp

set /a num*=m

set /a m-=1

if %m% neq 0 goto lp

:begin

set code=!codes: =!&set str=&set /a n=x

:again

set /a a=%random%%%%n%

set a=!code:~%a%,1!

set code=!code:%a%=!

set str=%str%%a%

set /a n-=1

if "!str:~%y%!" equ "" goto again

if exist temp.txt for /f "delims=" %%i in (temp.txt) do if "%%i" equ "%str%" goto begin

echo %str%>>temp.txt

set /a m+=1

if %m% lss %num% goto begin

cls&sort temp.txt&del /q temp.txt

pause>nul

Originally posted by pusofalse at 2008-6-29 11:07:
There are also bugs in the code provided by前辈 ZW... It can only arrange combinations of four characters. If there are more than a few, it only keeps the first four... If there are fewer, there will be an error of dividing by zero...
The number of randomly given strings is unknown...

The indeterminate number of characters is indeed a big problem. The following code basically achieves it (I think it's quite complicated):

@echo off&setlocal enabledelayedexpansion

if exist temp.txt del /q temp.txt

:enter

cls&set /p codes=Please enter the character group (separate characters with spaces):

if not defined codes goto enter

for %%i in (%codes%) do set /a m+=1

set /a num=1,x=m,y=m-1

:lp

set /a num*=m

set /a m-=1

if %m% neq 0 goto lp

:begin

set code=!codes: =!&set str=&set /a n=x

:again

set /a a=%random%%%%n%

set a=!code:~%a%,1!

set code=!code:%a%=!

set str=%str%%a%

set /a n-=1

if "!str:~%y%!" equ "" goto again

if exist temp.txt for /f "delims=" %%i in (temp.txt) do if "%%i" equ "%str%" goto begin

echo %str%>>temp.txt

set /a m+=1

if %m% lss %num% goto begin

cls&sort temp.txt&del /q temp.txt

pause>nul

Last edited by zw19750516 on 2008-6-29 at 12:04 PM ]

Thanks a lot! Learning~

Originally posted by pusofalse at 2008-6-29 11:35:
Thanks a lot! Learning~

Such a method will be terribly slow when the number of characters exceeds six! Still need to find other methods.

Hmm, it's tried. It's okay for less than 6 digits... Also, there's another bug. When entering a string like "b e e n" with two identical characters in it, it will go wrong.

/*本程序在TC2.0下运行通过*/

/*Algorithm 5.7 PERMUTATIONS1*/

#include<stdio.h>

int P;

void print(int P,int n)

{

	int i;

	printf("\n");

	for(i=1;i<=n;i++)

		printf("%d",P);

	sleep(1);

}



void perm1(int m,int n)

{

	int j,t;

	if(m==n)

		print(P,n);

	else

		for(j=m;j<=n;j++)

		{

			t=P;

			P=P;

			P=t;

			perm1(m+1,n);

			t=P;

			P=P;

			P=t;

		}

}



main()

{

	int j,n;

	clrscr();

	window(35,1,46,1);

	textbackground(4);

	textcolor(128);

	clrscr();

	printf("www.cndos.cn\n");

	printf("Please input the value of n:");

	scanf("%d",&n);

	for(j=1;j<=n;j++)

		P=j;

	perm1(1,n);

	printf("\nPress any key to end.");

	getch();

}

When I studied "Algorithm Design" before, I wrote such a C code, which is a recursive algorithm.

/*This program runs successfully under TC2.0*/

/*Algorithm 5.7 PERMUTATIONS1*/

#include<stdio.h>

int P;

void print(int P,int n)

{

	int i;

	printf("\n");

	for(i=1;i<=n;i++)

		printf("%d",P);

	sleep(1);

}



void perm1(int m,int n)

{

	int j,t;

	if(m==n)

		print(P,n);

	else

		for(j=m;j<=n;j++)

		{

			t=P;

			P=P;

			P=t;

			perm1(m+1,n);

			t=P;

			P=P;

			P=t;

		}

}



main()

{

	int j,n;

	clrscr();

	window(35,1,46,1);

	textbackground(4);

	textcolor(128);

	clrscr();

	printf("www.cndos.cn\n");

	printf("Please input the value of n:");

	scanf("%d",&n);

	for(j=1;j<=n;j++)

		P=j;

	perm1(1,n);

	printf("\nPress any key to end.");

	getch();

}

Characters that are the same are easy to handle:
Add in the batch processing "for %%i in (%codes%) do set a=#%%i#&set b=!b! !a!", and then make corresponding processing. The specific code I won't write. It's just that the efficiency of the high position seems to be unable to be solved with batch processing, because using the method of set var=%var% %str% in my second floor will be limited by the total number of characters.

Last edited by zw19750516 on 2008-6-29 at 12:02 PM ]

@echo off&setlocal enabledelayedexpansion

set s1=a b c

for %%a in (!s1!) do (set s2=!s1:%%a=!

  for %%b in (!s2!) do (set s3=!s2:%%b=!

    for %%c in (!s3!) do (echo %%a%%b%%c

) ) )

pause

```@echo off&setlocal enabledelayedexpansion
set s1=a b c
for %%a in (!s1!) do (set s2=!s1:%%a=!
for %%b in (!s2!) do (set s3=!s2:%%b=!
for %%c in (!s3!) do (echo %%a%%b%%c
) ) )
pause

The 6-digit code is similar to```

@echo off&setlocal enabledelayedexpansion

if exist pl.txt del /q pl.txt

:enter

cls&set /p codes=请输入三个以上的字符(字符应不相同并请用空格格开)：

if not defined codes goto enter

for %%i in (%codes%) do set /a m+=1

if %m% lss 3 set m=0&goto enter

cls&echo 正在排列中，请稍候...

set /a num1=1,x=m,y=m-1

:lp

set /a num1*=m,m-=1

if %m% neq 0 goto lp

set /a num2=num1/6+1,sz=1

:begin

set code=%codes: =%&set str=&set n=%x%

:again

set /a a=%random%%%%n%,n-=1

set a=!code:~%a%,1!

set str=%str%%a%&set code=!code:%a%=!

if "!str:~%y%!" equ "" goto again

for /l %%a in (1,1,%sz%) do (

    for %%i in (!var%%a!) do (

        if "%%i" equ "%str%" goto begin



   )

)

echo %str%>>temp.txt

set var%sz%=!var%sz%! %str%

set /a m+=1,z+=1

if %z% equ 6 set /a sz+=1,z=0

if %m% neq %num1% goto begin

sort temp.txt>pl.txt&del /q temp.txt&start pl.txt

Finally improved a little bit of efficiency, local test permuting six-digit numbers takes nearly 10 minutes:

@echo off&setlocal enabledelayedexpansion

if exist pl.txt del /q pl.txt

:enter

cls&set /p codes=Please enter three or more characters (characters should be different and please separate with spaces):

if not defined codes goto enter

for %%i in (%codes%) do set /a m+=1

if %m% lss 3 set m=0&goto enter

cls&echo Arranging, please wait...

set /a num1=1,x=m,y=m-1

:lp

set /a num1*=m,m-=1

if %m% neq 0 goto lp

set /a num2=num1/6+1,sz=1

:begin

set code=%codes: =%&set str=&set n=%x%

:again

set /a a=%random%%%%n%,n-=1

set a=!code:~%a%,1!

set str=%str%%a%&set code=!code:%a%=!

if "!str:~%y%!" equ "" goto again

for /l %%a in (1,1,%sz%) do (

    for %%i in (!var%%a!) do (

        if "%%i" equ "%str%" goto begin



   )

)

echo %str%>>temp.txt

set var%sz%=!var%sz%! %str%

set /a m+=1,z+=1

if %z% equ 6 set /a sz+=1,z=0

if %m% neq %num1% goto begin

sort temp.txt>pl.txt&del /q temp.txt&start pl.txt

@echo off&setlocal enabledelayedexpansion

set s1=a b c e d f g

set t=%time%

for %%a in (!s1!)do (set s2=!s1:%%a=!

  for %%b in (!s2!)do (set s3=!s2:%%b=!

    for %%c in (!s3!)do (set s4=!s3:%%c=!

      for %%d in (!s4!)do (set s5=!s4:%%d=!

        for %%e in (!s5!)do (set s6=!s5:%%e=!

          for %%f in (!s6!)do (set s7=!s6:%%f=!

            for %%g in (!s7!)do (echo %%a%%b%%c%%d%%e%%f%%g

) ) ) ) ) ) )

call timediff.bat %t% %time% 0

pause

7-bit takes 2.28 seconds
timediff.bat can be found in the forum p function library (used to calculate the difference between two time points)

@echo off&setlocal enabledelayedexpansion

set s1=a b c e d f g

set t=%time%

for %%a in (!s1!)do (set s2=!s1:%%a=!

  for %%b in (!s2!)do (set s3=!s2:%%b=!

    for %%c in (!s3!)do (set s4=!s3:%%c=!

      for %%d in (!s4!)do (set s5=!s4:%%d=!

        for %%e in (!s5!)do (set s6=!s5:%%e=!

          for %%f in (!s6!)do (set s7=!s6:%%f=!

            for %%g in (!s7!)do (echo %%a%%b%%c%%d%%e%%f%%g

) ) ) ) ) ) )

call timediff.bat %t% %time% 0

pause

Originally posted by plp626 at 2008-6-29 14:07:
7 characters took 2.28 seconds
timediff.bat can be found in the forum's p function library (used to calculate the difference between two time points)

@echo off&setlocal enabledelayedexpansion

set s1=a b c e d f g

set t=%time%

f ... 


The method is good, it's fast, but please clarify the original poster's intention: "The number of characters is not fixed".

Generate an n-layer nested bat and call it =.=

Bat seems to be able to achieve "recursion" using parameters... But I haven't practiced this... Brain cells...