Te paso este código, en C++, que imprime los numeros primos existentes hasta el numero ingresado. Es recursivo. La recursividad está en la función "SiPrimo".<br><br>Para demostrar que un numero es primo, basta con no encontrar divisores entre 2 y la parte entera de la raiz del numero dado.<br>
<br><span style="font-family: courier new,monospace;">#include <iostream></span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">#include <stdio.h></span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">#include <math.h></span><br style="font-family: courier new,monospace;"><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">using namespace std;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> </span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">bool SiPrimo (long int, long int);</span><br style="font-family: courier new,monospace;">
<br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">int main ()</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">{</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> system("cls");</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> </span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> int n;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> int raizDeN;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> bool primo;</span><br style="font-family: courier new,monospace;"><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> cout << endl << endl << "Numeros primos entre 2 y un valor ingresado.";</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> cout << endl << endl << "ingrese cualquier numero positivo: ";</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> cin >> n;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> cout << endl;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> cout << "los numeros primos entre 2 y " << n << " son:";</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> for(int i = 2; i <= n; i++)</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> {</span><br><span style="font-family: courier new,monospace;"> // calculo la raiz del numero en cuestión</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> raizDeN = (int)sqrt((double)i);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> // pregunto si es primo</span><br>
<span style="font-family: courier new,monospace;"> primo = SiPrimo(i, raizDeN);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> if(primo)</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> {</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> cout << endl;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> cout << i;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> } </span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;"><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> cout << endl; </span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> system("pause");</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> return 0;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">}</span><br style="font-family: courier new,monospace;"><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">// N es el número que estamos analizando<br>
// limSup es parte entera de la raiz de este numero<br>bool SiPrimo (long int N, long int limSup)</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">{</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> // si limSup es distinto de 1</span><br><span style="font-family: courier new,monospace;"> if(limSup != 1)</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> {<br>
</span><span style="font-family: courier new,monospace;"> // si la parte entera de la division entre N y limSup es distinta de cero</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> if(N % limSup != 0)</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> {</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> // por aca puede ser, pruebo el anterior.</span><br>
<span style="font-family: courier new,monospace;"> SiPrimo(N, limSup - 1);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> else</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> {</span><br><span style="font-family: courier new,monospace;"> // encontre un divisor, no es primo</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> return false;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> else</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> {</span><br><span style="font-family: courier new,monospace;"> // llegue hasta 1 sin encontrar divisores, es primo</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> return true;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">}</span><br><cite><span style="font-family: courier new,monospace;"></span><br><br clear="all"></cite>Saludos.<br><br>(\__/)<br>(='.'=)<br>(")_(")<br>Este es Conejito. <br>
Copia y pega a Conejito en tu firma para ayudarlo a dominar el mundo.<br>
<br><br><div class="gmail_quote">2009/11/9 Adrian Vargas <span dir="ltr"><<a href="mailto:adrianvargas10@hotmail.com">adrianvargas10@hotmail.com</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>
Hola a todos soy un joven estudiante de Ing Mecatronica, apenas empezando, pero ya tengo problemas al programar.. bueno mi problema es como definir, como escribir en el lenguaje de programcion (algoritmos) un numero primo, como lo defino? como le enseño al computador? por que en teoria un numero primo es aquel ke es divisible por el mismo y por uno, pero no se como escribir eso en c++.. de antemano saludos y gracias a kien pueda ayudarme..<br>
<br><div>
<p align="center"><font size="7" color="#000033" face="Courier New, Courier, Monospace"><b> </b></font></p>
<p align="center"><font size="7" face="Verdana, Geneva, Arial, Sans-serif"></font> </p>
<p align="center"><font size="7" face="Verdana"><font face="Times New Roman">>>>>><img style="width: 15px; min-height: 19px;" src="http://graphics.hotmail.com/i.p.embeer.gif" height="19" width="19">[JETMAN]</font><font color="#ff0000"><img style="width: 15px; min-height: 19px;" src="http://graphics.hotmail.com/i.p.embeer.gif" height="19" width="19"></font></font></p>
</div><br><br><br><br><br> <br><hr>Invite your mail contacts to join your friends list with Windows Live Spaces. It's easy! <a href="http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=en-us" target="_blank">Try it!</a></div>
<br>_______________________________________________<br>
Lista de correo Cconclase <a href="mailto:Cconclase@listas.conclase.net">Cconclase@listas.conclase.net</a><br>
<a href="http://listas.conclase.net/mailman/listinfo/cconclase_listas.conclase.net" target="_blank">http://listas.conclase.net/mailman/listinfo/cconclase_listas.conclase.net</a><br>
Bajas: <a href="http://listas.conclase.net/index.php?gid=2&mnu=FAQ" target="_blank">http://listas.conclase.net/index.php?gid=2&mnu=FAQ</a><br></blockquote></div><br>