[C++] Random string - Newbie

[|G3|]

The function "randmG" will generate random letters.
I made this using dev c++, so if you're using Visual then some stuff might be different, I dunno.
I'm still learning C++, so this might not be a good way of generating a random string. So if you know more >>, tell me what I should improve on or w/e.

#include <cstdlib>
#include <iostream>
#include <string.h>

using namespace std;
string randmG(int lenght);

int main(int argc, char *argv[])
{
    string randm;
    int lent;

    cout << "Please enter how long the random string should be:";
    cin >> lent;
    randm = randmG(lent);
    cout << "Random string generated: " << randm << endl;
    cout << "Press enter to exit.."<< endl;
    cin.get();
    cin.get();
    return 0;
}

string randmG(int lenght)
{
       string G;
       int i = 0;
       int n;
       
       srand(time(NULL));
       for(n=0; n<lenght; n++)
       {
               i = rand() % 26;
               G += (char)(i+65);
       }
       return G;
}

[Check]

I usually use this.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define STRING_SIZE 32
#define LETTER 26
#define NUMBER 10

static char random_letter(int is_cap)
{
   int letter = (int)(LETTER * (rand() / (RAND_MAX + 1.0)));
   return((char)((is_cap == 1) ? (letter + 65) : (letter + 97)));
}

static char random_number()
{
   int number = (int)(NUMBER * (rand() / (RAND_MAX + 1.0)));
   return((char)(number + 48));
}

static void random_string(int length, char *str)
{
   int i;
   int char_type;
   
   for(i = 0; i < length; i++)
   {
      char_type = (int)(3 * (rand() / (RAND_MAX + 1.0)));
      
      switch(char_type)
      {
      case 0:
         str[i] = random_letter(0);
         break;
      case 1:
         str[i] = random_letter(1);
         break;
      case 2:
         str[i] = random_number();
         break;
      default:
         str[i] = random_number();
         break;
      }
   }  
}

int main(int argc, char *argv[])  
{
   char random_str[STRING_SIZE + 1];

   srand((unsigned)time(NULL));

   random_str[STRING_SIZE] = '\0';

   random_string(STRING_SIZE, random_str);

   printf("Random string %d characters long. [%s]\n", STRING_SIZE, random_str);
   
   return(0);