i want to print the following sequence of latters...

A

B

C

.

.

Z

AA

AB

AC

.

.

AZ

BA

BB

BC

. . .

ZZ

. . .

ZZZ

. . .

ZZZZ

up to any given length of word.

How to do it?

my try…

int main()
{
	vector<string> words;

	char ch0[2] = { 'A', '\0' };

	for (int i = 0; i < 26; i++)
	{
		const char ch = 'A' + i;

		string str = string(1, ch0[0]);

		str += string(1, ch);

		words.push_back(str);

	}

	ofstream outfile("allwords.txt");

	for (int i = 0; i < 26; i++)
	{
		outfile << words[i] << endl;
	}

	outfile.close(); 

	system("pause");
	return 0;
}

I am really surprised that anyone actually needs this. Perl provides this functionality just by using operator ++ on a string of letters.

$x = "A";
print $x++."\n" while 1;

In C++ you can implement a similar operation like this:

#include <iostream>
#include <string>
#include <cstdlib>

void increment(std::string &s) {
  for (auto i = s.rbegin(); i != s.rend(); ++i) {
    if ('A' <= *i && *i < 'Z') {
      ++*i;
      return;
    }
    if (*i == 'Z')
      *i = 'A';
    else {
      std::cerr << "Found unexpected character '" << *i << "'\n";
      std::exit(1);
    }
  }
  s += 'A';
}

int main() {
  std::string x = "A";
  while (1) {
    std::cout << x << '\n';
    increment(x);
  }
}

alvaro said:

I am really surprised that anyone actually needs this. Perl provides this functionality just by using operator ++ on a string of letters.

$x = "A";
print $x++."\n" while 1;

In C++ you can implement a similar operation like this:

#include <iostream>
#include <string>
#include <cstdlib>

void increment(std::string &s) {
  for (auto i = s.rbegin(); i != s.rend(); ++i) {
    if ('A' <= *i && *i < 'Z') {
      ++*i;
      return;
    }
    if (*i == 'Z')
      *i = 'A';
    else {
      std::cerr << "Found unexpected character '" << *i << "'\n";
      std::exit(1);
    }
  }
  s += 'A';
}

int main() {
  std::string x = "A";
  while (1) {
    std::cout << x << '\n';
    increment(x);
  }
}

great man, thanks…

Here's a recursive version.

#include <iostream>
#include <string>

void PrintABC(int iDepth, std::string szAlpha)
{
   if (iDepth == 0) {
      std::cout << szAlpha << std::endl;
   } else {
      for (char c='A'; c<='Z'; ++c) {
         szAlpha.push_back(c);
         PrintABC(iDepth-1,szAlpha);
         szAlpha.pop_back();
      }
   }
}

int main()
{
   int iMaxDepth;
   std::string szALpha;

   std::cout << "Enter maximum length: ";
   std::cin >> iMaxDepth;
   std::cout << std::endl;

   for (int iDepth = 1; iDepth<=iMaxDepth; ++iDepth) {
      PrintABC(iDepth,szALpha);
      std::cout << std::endl;
   }
   return 0;
}

Good ol' homework…