This solution is OK. But it not satisfy the restrictions.
Your tests are too weak.

#include <iostream>
int main(int argc, char* argv[])
{
    int i= 0;
    for (i = 0; i < 1000000; i++)
            {
                printf("%c", rand()%26 + 'a');
            }
    return 0;
}

This problem can be solved without random exirsices :)
I have got AC just by writing triads in order(without spaces):
aaa aab aac aad... aba abb abc abd... zzz. I did it recursivly. And then you must repeat this sequence until number of characters=10^6;

Buning uchun rand() funksiyasidan foydalaning.
masalan:
1000000 ta ababababbabab.....asdbasdsajkdbksajbdjkasbdkjbskfjbaksjdbfkjsad.
faqat ixtiyoriy ravishda bo'lsin

k = rand()%26 + 97 ;
qilib chiqaring shuni uzi kifoya

Edited by author 15.06.2013 11:32

#include <bits/stdc++.h>
using namespace std;

int main() {
    string letter="abcdefghijklmnopqrstuvwxyz";
    int k=letter.size();
    int i1,i2,i3;
    string part,bigpart;
    for(i1=0;i1<k;i1++)
    {
        for(i2=0;i2<k;i2++)
        {
            for (i3=0;i3<k;i3++)
            {
                part="";
                part.pb(letter[i1]);
                if(part[0]!=letter[i2]) part.pb(letter[i2]); else continue;
                if(part[0]!=letter[i3]&&part[1]!=letter[i3]) part.pb(letter[i3]); else continue;
                bigpart.pb(letter[i1]);bigpart.pb(letter[i2]);bigpart.pb(letter[i3]);
            }
        }
    }
    string ans="";
    //cout<<bigpart.size()/3;
    while(ans.size()<1000000)
    {
        ans=ans+bigpart;
    }
    /*for (int i=0;i<1000000;i++)
    {
        cout<<ans[i];
    }*/
    int res=0;
    for (int i=0;i<1000000;i++)
    {
        if (ans.substr(i,1)=="a") res++;
    }
    cout<<res;
    return 0;
}

Maybe 1 test is a sort of tricky?

Edited by author 06.04.2017 01:18

Are you sure you really mean "subsequence" and not "substring"?

You can use "random" function to produce a letter.

var i:longint;

function car(k:longint):char;
begin
car:=chr(k+ord('a'));
end;

begin
for i:=0 to 333332 do
 begin
 write(car((i div 676) mod 26),car((i div 26) mod 26),car(i mod 26));
 end;
write('a');
end.

Why do I have this error occurs in Python 3.x solution?

You can find discussion about solution in python of this problem here: http://stackoverflow.com/q/16308989/609857

public class T_1219_Symbolic_Sequence {
public static void main(String[] args) {
PrintWriter pw= new PrintWriter(new OutputStreamWriter(System.out));
Random r= new Random();    char a[]=new char[30];    int k = 0 ;
  for (char j ='a'; j <='z'; j++)
     a[++k]=j;
    for (int i = 1; i <=1000000; i++)
        pw.print(a[r.nextInt(26)+1]);
    pw.close();
}
}

#include<iostream>
#include<cstdlib>
using namespace std;
int main(){
int i,j,n,m,k;
for(i=0;i<1000000;i++){
k=rand()%26;
k+=97;
cout<<(char)k;
}
//cin.get();
return 0;
}

#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
int main()
{
int i=1;
srand((unsigned)time(0));
char random_integer;
while(i<=1000000)
{
random_integer = (rand()%'z')+1;
if(random_integer>='a'&& random_integer<='z')
{
cout << random_integer;
i++;
}}
cout<<endl;
return 0;
}

Edited by author 10.04.2009 16:54

As you can see the task is to output the sequence consists of 1000000
symbols. I output exactly 1000000 symbols one by one (...Write
(sym)...Write(sym)...Write(sym)...), buf after 0.04 seconds I
receive "Output Limit". What does it mean and how should I output the
sequence?
Please, help me!

look at my program:

program u1219;

var
  a:array[1..26] of char;
  i:longint;

begin
  randomize;

  for i:=1 to 26 do
    a[i]:=chr(ord('a')+i-1);

  for i:=1 to 1000000 do
    write(a[random(26)+1]);
end.

too unbelievable!!!

Just random =)))

Is my algo wrong?
This is my solution


# include <stdio.h>
main()
{
    int i=0,m,g,k=0;
    const int n=100000;
//    const char AZ[26]={'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'};
    const char az[26]={'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'};
    while(i!=n)
    {
        for(m=k;m+k<26&&i<n;m++)
            for(g=0;g<26&&i<n;g++)
            {
                printf("%c",az[m%26]);
                i++;
                printf("%c",az[g]);
                i++;
            }
        k++;
        k%=26;
    }
    return 0;
}

program SymbolicSequence; {.$APPTYPE CONSOLE}
var
    RndSeed: LongInt;

function MyRandom(Range: Integer): Integer;
var
    RDouble: Extended;
begin
    MyRandom := (RndSeed div 10000) mod Range;

    RDouble := RndSeed;
    RDouble := (RDouble * 3141592621 + 184421);
    RDouble := RDouble - $7FFFFFFF*Int(RDouble/$7FFFFFFF);
    RndSeed := Trunc(RDouble);
end;

var
    i: Integer;
begin
    RndSeed := 98586100;
    for i := 1 to 1000000 do
        Write(Chr(MyRandom(26) + Ord('a')));
    WriteLn;
end.

{ The tester program  }
program test; {$APPTYPE CONSOLE}
const
    OneCnt = 39000;
    TwoCnt = 1600;
    TriCnt = 97;

var
    i: Integer;
    S: String[4];
    Use1: array['a'..'z'] of Word;
    Use2: array['a'..'z', 'a'..'z'] of Word;
    Use3: array['a'..'z', 'a'..'z', 'a'..'z'] of Word;

    Ch: Char;
begin
    FillChar(Use1, SizeOf(Use1), 0);
    FillChar(Use2, SizeOf(Use2), 0);
    FillChar(Use3, SizeOf(Use3), 0);

    S := '123';
    Read(S[1], S[2], S[3]);
    Inc(Use1[S[1]]);
    Inc(Use1[S[2]]);
    Inc(Use1[S[3]]);

    Inc(Use2[S[1], S[2]]);
    Inc(Use2[S[2], S[3]]);

    Inc(Use3[S[1], S[2], S[3]]);

    for i := 4 to 1000000 do
    begin
        Read(Ch);
        if Ch in ['a'..'z'] then
        begin
            Delete(S, 1, 1);
            S := S + Ch;

            Inc(Use1[S[3]]);
            Inc(Use2[S[2], S[3]]);
            Inc(Use3[S[1], S[2], S[3]]);

            if Use1[S[3]] > OneCnt then
            begin
                WriteLn('Letter ', S[3], ' used more than ',
                          OneCnt, ' times!!!');
                Halt;
            end;

            if Use2[S[2], S[3]] > TwoCnt then
            begin
                WriteLn('Digraph ', S[2],S[3], ' used more than ',
                       TwoCnt, ' times!!!');
                Halt;
            end;

            if Use3[S[1], S[2], S[3]] > TriCnt then
            begin
                WriteLn('Trigraph ', S[1],S[2],S[3],
                        ' used more than ', TriCnt, ' times!!!');
                Halt;
            end;
        end else
        begin
            WriteLn('Error!!!');
            WriteLn('Not small latin letter at ', i);
            Halt;
        end;
    end;

    WriteLn('Ok');
end.

Just look at my program:

[code deleted]

Edited by moderator 02.01.2007 18:52