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

{$H}
const fi='';
      fo='';
      maxn=101;
type ar=array[1..maxn] of string;
var n,k,test,it,maxnum,num:longint;
    a,aa,b,d,dd,e,h:array[1..maxn] of longint;
    c,g:ar;
    f:array[0..maxn,0..maxn,0..9] of longint;
    kt:boolean;
    kq,temp:string;

procedure rf;
var i,j:longint;
    s:string;
begin
     read(n,k);
     for i:=1 to n do read(a[i]);
     for i:=1 to n-1 do
         for j:=i+1 to n do
             if a[i]>a[j] then
             begin
                  a[i]:=a[i]+a[j];
                  a[j]:=a[i]-a[j];
                  a[i]:=a[i]-a[j];
             end;
     for i:=1 to n do
     begin
          str(a[i],g[i]);
          d[i]:=length(g[i]);
          h[i]:=i;
     end;
end;

function min(x,y:longint):longint;
begin
     if x<y then min:=x else min:=y;
end;

function getmax(x,y:longint):longint;
begin
     if x>y then getmax:=x else getmax:=y;
end;

function comp(y,x:string):longint;
var i,lx,ly:longint; t:string;
begin
     lx:=length(x); ly:=length(y); comp:=0;
     while true do
     begin
          if lx<ly then
          begin
               t:=copy(y,1,min(lx,ly));
               delete(y,1,min(lx,ly));
               if t<x then exit(-1)
               else
               begin
                    if t>x then exit(1);
               end;
               ly:=length(y);
               if ly=0 then exit;
          end
          else
          begin
               t:=copy(x,1,min(lx,ly));
               delete(x,1,min(lx,ly));
               if y<t then exit(-1)
               else
               begin
                    if y>t then exit(1);
               end;
               lx:=length(x);
               if lx=0 then exit;
          end;
     end;
end;

procedure sort3(l,r:longint);
var i,j,y,t:longint; x,u:string;
begin
     i:=l; j:=r; x:=g[(i+j) shr 1]; y:=h[(i+j) shr 1];
     repeat
           while (comp(g[i],x)=-1) or ((comp(g[i],x)=0) and (h[i]<y)) do inc(i);
           while (comp(g[j],x)=1) or ((comp(g[j],x)=0) and (h[j]>y)) do dec(j);
           if i<=j then
           begin
                u:=g[i]; g[i]:=g[j]; g[j]:=u;
                t:=h[i]; h[i]:=h[j]; h[j]:=t;
                inc(i); dec(j);
           end;
     until i>j;
     if i<r then sort3(i,r);
     if l<j then sort3(l,j);
end;

procedure trace;
var dem,i,max,j:longint;
begin
     fillchar(b,sizeof(b),0);
     dem:=k;
     kt:=false; max:=1;
     num:=0;
     for i:=n downto k do
         if f[i,k,0]>max then
         begin
              num:=1; e[num]:=i;
              max:=f[i,k,0];
              kt:=true;
         end
         else
         begin
              if f[i,k,0]=max then
              begin
                   inc(num); e[num]:=i;
              end;
         end;
     if not kt then exit;
     kq:=''; j:=0;
     i:=e[1];
     repeat
           if f[i,dem,j]-d[i]=f[i-1,dem-1,(j+9-a[i] mod 9) mod 9] then
           begin
                dec(dem);
                j:=(j+9-a[i] mod 9) mod 9;
                if (dem=0) and (j<>0) then
                begin
                     inc(dem);
                     j:=(j+a[i]) mod 9;
                end
                else b[k-dem]:=a[i];
           end;
           dec(i);
     until dem=0;
     for i:=1 to k do write(b[i]);
end;

procedure pr;
var i,j,p,q:longint;
begin
     fillchar(f,sizeof(f),false);
     f[0,0,0]:=1;
     for i:=1 to n do
         for j:=0 to min(i,k) do
                 for q:=0 to 9 do
                 begin
                      f[i,j,q]:=f[i-1,j,q];
                      if j>0 then
                      begin
                           p:=f[i-1,j-1,(q+9-a[i] mod 9) mod 9];
                           if p>0 then f[i,j,q]:=getmax(f[i,j,q],p+d[i]);
                      end;
                 end;
end;

procedure edit;
var i:longint;
begin
     sort3(1,n);
     aa:=a; dd:=d;
     for i:=1 to n do
     begin
          a[i]:=aa[h[i]];
          d[i]:=dd[h[i]];
     end;
end;

procedure wf;
var i:longint;
begin
     if not kt then writeln(-1)
     else writeln(kq);
end;

begin
     assign(input,fi); reset(input);
     assign(output,fo); rewrite(output);
     read(test);
     for it:=1 to test do
     begin
          rf;
          edit;
          pr;
          trace;
          wf;
     end;
     close(input); close(output);
end.

Code mẫu của ladpro98

{$H+}
program FindingPassword;
uses    math,sysutils;
const   maxn=111;
        fi='';
var     a:array[1..maxn] of longint;
        str:array[1..maxn] of string;
        f:array[0..maxn,0..maxn,0..8] of string;
        exist:array[0..maxn,0..maxn,0..8] of boolean;
        inp:text;
        t,tt,n,k,i,j,r:longint;
        x,y,z:string;

procedure sort(l,r:longint);
var     i,j,t:longint;
        p:string;
begin
        if l>=r then exit;
        i:=l;j:=r;
        p:=IntToStr(a[random(r-l+1)+l]);
        repeat
                while IntToStr(a[i])+p>p+IntToStr(a[i]) do inc(i);
                while IntToStr(a[j])+p<p+IntToStr(a[j]) do dec(j);
                if i<=j then
                begin
                        if i<j then
                        begin
                                t:=a[i];
                                a[i]:=a[j];
                                a[j]:=t;
                        end;
                        inc(i);dec(j);
                end;
        until i>j;
        sort(l,j);sort(i,r);
end;

function comp(var a,b:string):boolean;
begin
        if length(a)<length(b) then exit(true);
        if length(a)>length(b) then exit(false);
        exit(a<b);
end;

begin
        assign(inp,fi);reset(inp);
        readln(inp,t);
        for i:=0 to maxn do exist[i,0,0]:=true;
        for tt:=1 to t do
        begin
                readln(inp,n,k);
                for i:=1 to n do readln(inp,a[i]);
                sort(1,n);
                for i:=1 to n do Str[i]:=IntToStr(a[i]);

                for i:=1 to n do
                for j:=1 to i do
                for r:=0 to 8 do
                begin
                        f[i,j,r]:='';
                        if exist[i-1,j-1,(9+r-a[i] mod 9) mod 9] then
                        f[i,j,r]:=f[i-1,j-1,(9+r-a[i] mod 9) mod 9]+Str[i];
                        if exist[i-1,j,r] and comp(f[i,j,r],f[i-1,j,r]) then f[i,j,r]:=f[i-1,j,r];
                        if exist[i,j-1,r] and comp(f[i,j,r],f[i,j-1,r]) then f[i,j,r]:=f[i,j-1,r];
                        if f[i,j,r]<>'' then exist[i,j,r]:=true
                        else exist[i,j,r]:=false;
                end;
                if not exist[n,k,r] then writeln(-1)
                else    writeln(f[n,k,0]);
        end;
end.

Code mẫu của RR

{$MODE OBJFPC}

uses math;
const
  FINP          =       '';
  FOUT          =       '';
  MAXN          =       111;

var
  f1,f2         :       text;
  test,n,k      :       longint;
  f             :       array[1..MAXN,0..MAXN,0..8] of longint;
  a             :       array[1..MAXN] of longint;

procedure openF;
    begin
      assign(f1,FINP); reset(f1);
      assign(f2,FOUT); rewrite(f2);
    end;

procedure closeF;
    begin
      close(f1);
      close(f2);
    end;

procedure inp;
    var
      i:longint;
    begin
      read(f1,n,k);
      for i:=1 to n do
        read(f1,a[i]);
    end;

var
  s1,s2:string[20];

function lower(a,b:longint):boolean;
    begin
      str(a,s1); str(b,s2);
      exit( s1+s1 < s2+s2 );
    end;

procedure init;
    var
      i,j,tmp:longint;
    begin
      fillchar(f,sizeof(f),$FF);
      for i:=1 to n-1 do
      for j:=i+1 to n do
        if lower(a[i],a[j]) then
          begin
            tmp:=a[i];
            a[i]:=a[j];
            a[j]:=tmp;
          end;
    end;

procedure solve;
    var
      i,c,next,du:longint;
      s:string[10];
    begin
      f[n+1,0,0]:=0;
      for i:=n downto 1 do
        begin
          //Ko chon a[i]
          for c:=0 to k do
          for next:=0 to 8 do
          if f[i+1,c,next]>=0 then
            f[i,c,next]:=f[i+1,c,next];

          //Chon a[i]
          str(a[i],s);
          f[i,1,a[i] mod 9]:=max(f[i,1,a[i] mod 9],length(s));
          for c:=0 to k-1 do
          for next:=0 to 8 do
          if f[i+1,c,next]>=0 then
            f[i,c+1,(next+a[i]) mod 9]:=max(f[i+1,c,next]+length(s),f[i,c+1,(next+a[i]) mod 9]);
        end;

      if f[1,k,0]<0 then begin writeln(f2,-1); exit; end;

      du:=0;
      for i:=1 to n do
        begin
          if k=0 then break;
          str(a[i],s);
          if f[i+1,k-1,(du+9-a[i] mod 9) mod 9]+length(s)=f[i,k,du] then
            begin
              write(f2,a[i]);
              dec(k); du:=(du+9-a[i] mod 9) mod 9;
            end;
        end;
      writeln(f2);
    end;

begin
  openF;
  read(f1,test);
  for test:=1 to test do
    begin
      inp;
      init;
      solve;
    end;
  closeF;
end.

Code mẫu của hieult

#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<cassert>
#include<ctime>
#include<algorithm>
#include<iterator>
#include<iostream>
#include<cctype>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<list>
//#include<conio.h>
#define ep 0.000000001
#define maxn 111
#define oo 1111111111
#define base 100000000
#define TR(c, it) for(typeof((c).begin()) it=(c).begin(); it!=(c).end(); it++)
double const PI=4*atan(1);

using namespace std;

typedef pair<int, int> II;
typedef vector<int> VI;
typedef vector<II> VII;
typedef vector<VI> VVI;
typedef vector<VII> VVII;

int main ()
{
   // freopen("FP.in","r",stdin);
  int test,n,k,so,du;  
  string S[10][111],s[111],the1,the2,temp;
  scanf("%d",&test);
  for(int itest = 1;itest<=test;itest++){
       scanf("%d %d",&n,&k);
       for(int i = 1;i<=n;i++) cin>>s[i];
       for(int i = 1;i<=n;i++)
             for(int j = i+1;j<=n;j++){
                  the1 = s[i]+s[j];
                  the2 = s[j]+s[i];
                  if(the1.compare(the2)<0){
                        temp = s[i];
                        s[i] = s[j];
                        s[j] = temp;
                  }
             }
       //for(int i = 1;i<=n;i++) cout<<s[i]<<endl;
       for(int i = 0;i<9;i++) for(int j = 0;j<=n;j++) S[i][j]="";
       for(int i = 1;i<=n;i++){
             so = 0;
             for(int j = 0;j<s[i].length();j++)
                   so+=s[i][j]-'0';
             so%=9;
             for(int j = k;j>=2;j--){
                   for(int t = 0;t<9;t++){
                         if(S[t][j-1].compare("")!=0){
                               temp = S[t][j-1]+s[i];
                               du = (so+t)%9;
                               if((temp.length()>S[du][j].length())||((temp.length()==S[du][j].length())&&(temp.compare(S[du][j]))>0))
                                     S[du][j] = temp;
                         }
                   }
             }
             if((s[i].length()>S[so][1].length())||((s[i].length()==S[so][1].length())&&(s[i].compare(S[so][1]))>0)){
                  S[so][1] = s[i];
             }

       }
       if(S[0][k].compare("")==0)
             printf("-1\n");
       else cout<<S[0][k]<<endl;
  }
  //getch();
}