Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

var d:array['A'..'Z'] of byte;
    com:array[1..9,0..9] of longint;
    s:string;
    n:byte;
    dem:longint;

procedure init;
var i,j:byte; c:char;
begin
     fillchar(com,sizeof(com),0);
     for i:=1 to n do
     begin
          com[i,0]:=1; com[i,i]:=1;
     end;
     for i:=2 to n do
         for j:=1 to i-1 do
             com[i,j]:=com[i-1,j]+com[i-1,j-1];
     dem:=1;
     i:=n;
     for c:='A' to 'Z' do
         if d[c]>0 then
         begin
              dem:=dem*com[i,d[c]];
              i:=i-d[c];
         end;
end;

procedure rf;
var c:char;
begin
     n:=0;
     fillchar(d,sizeof(d),0);
     while not eof do
     begin
          inc(n);
          read(c);
          inc(d[c]);
     end;
end;

procedure att(i:byte);
var c:char; j:byte;
begin
     for c:='A' to 'Z' do
     begin
          if d[c]>0 then
          begin
               dec(d[c]);
               s:=s+c;
               if i<n then att(i+1)
               else writeln(s);
               inc(d[c]);
               delete(s,i,1);
          end;
     end;
end;

procedure pr;
var i:byte;
begin
     init;
     s:='';
     writeln(dem);
     att(1);
end;

begin
     rf;
     pr;
end.

Code mẫu của happyboy99x

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef vector<int> vi;
typedef vector<vi> vvi;

#define sz(a) int((a).size())
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(), (c).end()
#define tr(c,i) for(typeof((c).begin()) i = (c).begin(), _e = (c).end(); i != _e; ++i)
#define present(c,x) ((c).find(x) != (c).end())
#define cpresent(c,x) (find(all(c),x) != (c).end())
#define rep(i,n) for(int i = 0, _n = (n); i < _n; ++i)
#define repd(i,n) for(int i = (n)-1; i >= 0; --i )
#define fo(i,a,b) for(int i = (a), _b = (b); i <= _b; ++i)
#define fod(i,a,b) for(int i = (a), _b = (b); i >= _b; --i)

#define INF 1000000000
#define N

int main() {
    string s; cin >> s;
    vector<string> v; sort(all(s)); v.pb(s);
    while(next_permutation(all(s))) v.pb(s);
    printf("%d\n",v.size());
    tr(v,it) puts(it->c_str());
    return 0;
}

Code mẫu của ladpro98

program qbhv;
uses    math;
const   fi='';
var     ch:array['A'..'Z'] of longint;
        gt:array[1..10] of longint;
        res:array[1..10] of char;
        s:string[11];
        inp:text;
        len,counter:longint;

procedure input;
begin
        assign(inp,fi);
        reset(inp);
        readln(inp,s);
        len:=length(s);
        close(inp);
end;

procedure init;
var     i:longint;
begin
        for i:=1 to len do
        begin
                inc(ch[s[i]]);
        end;
        gt[1]:=1;
        for i:=2 to 9 do
        gt[i]:=gt[i-1]*i;
end;

procedure calc;
var     c:char;
begin
        counter:=gt[len];
        for c:='A' to 'Z' do
        if ch[c]>0 then
        counter:=counter div gt[ch[c]];
end;


procedure print;
var     i:longint;
begin
        for i:=1 to len do
        write(res[i]);
        writeln;
end;


procedure duyet(i:longint);
var     c:char;
begin
        if i>len then
        begin
                print;
                exit;
        end;
        for c:='A' to 'Z' do
        if ch[c]>0 then
        begin
                dec(ch[c]);
                res[i]:=c;
                duyet(i+1);
                inc(ch[c]);
        end;
end;

begin
        input;
        init;
        calc;
        writeln(counter);
        duyet(1);
end.

Code mẫu của RR

var
  cnt:longint;
  a:string;

function find:longint;
    var
      i:longint;
    begin
      for i:=length(a)-1 downto 1 do
        if a[i]<a[i+1] then exit(i);
      exit(0);
    end;

procedure sort(start,last:longint);
    var
      i,j:longint;
      tmp:char;
    begin
      for i:=start to last-1 do
      for j:=i+1 to last do
      if a[j]<a[i] then
        begin
          tmp:=a[i];
          a[i]:=a[j];
          a[j]:=tmp;
        end;
    end;

procedure gen(print:boolean);
    var
      i,j,ln:longint;
      tmp,c:char;
    begin
      i:=find;
      cnt:=1; if print then writeln(a);
      while i<>0 do
        begin
          ln:=i;
          for j:=i to length(a) do
            if (a[j]>a[i]) and ((a[j]<a[ln]) or (ln=i)) then ln:=j;

          tmp:=a[ln]; a[ln]:=a[i]; a[i]:=tmp;
          sort(i+1,length(a));
          i:=find;
          inc(cnt); if print then writeln(a);
        end;
    end;

begin
  readln(a);
  sort(1,length(a));

  gen(false);
  writeln(cnt);
  sort(1,length(a));
  gen(true);
end.

Code mẫu của ll931110

Program QBHV;
        Const
                input  = '';
                output = '';
        Var
                s: string;
                n: integer;
                x: array[1..9] of char;
                d: array['A'..'Z'] of integer;
              fac: array[0..9] of longint;
            fi,fo: text;

Procedure openfile;
          Begin
                Assign(fi, input);
                        Reset(fi);

                Assign(fo, output);
                        Rewrite(fo);
          End;

Procedure init;
          Var
                i: integer;
          Begin
                Readln(fi, s);
                n:= length(s);

                Fillchar(d, sizeof(d), 0);
                For i:= 1 to n do inc(d[s[i]]);
          End;

Procedure factorial;
          Var
                i: integer;
          Begin
                fac[0]:= 1;
                For i:= 1 to 9 do fac[i]:= fac[i - 1] * i;
          End;

Procedure number;
          Var
                res: longint;
                 ch: char;
          Begin
                res:= fac[n];
                For ch:= 'A' to 'Z' do res:= res div fac[d[ch]];
                Writeln(fo, res);
          End;

Procedure printresult;
          Var
                i: integer;
          Begin
                For i:= 1 to n do write(fo, x[i]);
                Writeln(fo);
          End;

Procedure attempt(i: integer);
          Var
                ch: char;
          Begin
                For ch:= 'A' to 'Z' do
                        if d[ch] > 0 then
                                Begin
                                        x[i]:= ch;

                                        If i = n then printresult else
                                                Begin
                                                        dec(d[ch]);
                                                        Attempt(i + 1);
                                                        inc(d[ch]);
                                                End;
                                End;
          End;

Procedure closefile;
          Begin
                Close(fi);
                Close(fo);
          End;

Begin
        openfile;
        init;
        factorial;
        number;
        attempt(1);
        closefile;
End.

Code mẫu của skyvn97

#include<stdio.h>
#include<string.h>
#define MAXL   20
#define MAXP   362890
long cntp;
int n;
char s[MAXL];
int perm[MAXP][MAXL];
int cnt[MAXL+20];
int cx[MAXL+20];
int x[MAXL];
void init(void)
{
     gets(s);
     int i;
     n=strlen(s);
     for (i=0;i<n;i=i+1)
         cnt[s[i]-64]++;
     cntp=0;
}
void save(void)
{
     cntp++;
     int i;
     for (i=1;i<=n;i=i+1) perm[cntp][i]=x[i];
}
void btrk(int k)
{
     int i;
     for (i=1;i<=30;i=i+1)
         if (cx[i]+1<=cnt[i])
            {
             x[k]=i;             
             cx[i]++;
             if (k==n) save();
             else btrk(k+1);
             cx[i]--;
            }
}
void print(void)
{
     printf("%ld\n",cntp);
     long i,j;
     for (i=1;i<=cntp;i=i+1)
         {
          for (j=1;j<=n;j=j+1) printf("%c",perm[i][j]+64);
          printf("\n");
         }
}
int main(void)
{
    init();
    btrk(1);
    print();
}

Code mẫu của khuc_tuan

#include <stdio.h>
#include <iostream>
using namespace std;

int main() {
    char a[100];
    gets(a);
    int na = strlen(a);
    sort( a, a+na);
    int dem = 0;
    do { ++dem; } while(next_permutation(a,a+na));
    sort( a, a+na);
    printf("%d\n", dem);
    do { puts(a); } while(next_permutation(a,a+na));
    return 0;
}