Array to Vector

[Joshcannon]

How would I go about changing this program of arrays into one with vectors?

 /*  --------------------------------------------------------
    This program uses a "char" array & the method known as
    “the Sieve of Erastosthenes” to determine & print all
    prime numbers up to 1000.
    -------------------------------------------------------- */

#include <cstdlib>
#include <iostream>

using namespace std ;

/*  --------------------------------------------------------
    Function initializeNumbers sets numbers 0 & 1 to Ignore,
    and sets numbers 2 & above to Unvisited.
    -------------------------------------------------------- */
void initializeNumbers ( char number[], int ARRAY_SIZE )
  {
  number[0]  =  'I' ; // 'I' means Ignore
  number[1]  =  'I' ;

  for ( int i = 2 ; i < ARRAY_SIZE ; i ++ )
    number[i]  =  'U' ; // 'U' means Unvisited
  } // end initializeNumbers function

/*  --------------------------------------------------------
    Function indexOfLeastU returns the least index such that
    the character stored at that index is 'U', with the
    exception that -1 is returned if no array element has
    value 'U'.
    -------------------------------------------------------- */
int indexOfLeastU ( char number[], int ARRAY_SIZE )
  {
  for ( int i = 0 ; i < ARRAY_SIZE ; i ++ )
    if ( number[i] == 'U' )
      return  i ;

  return  -1 ;
  } // end indexOfLeastU function

/*  --------------------------------------------------------
    Function identifyPrimes identifies which numbers are
    prime by placing 'P's at those indices.
    Composite #'s are marked with 'C's.
    -------------------------------------------------------- */
void  identifyPrimes ( char number[], int ARRAY_SIZE )
  {
  int  leastU  =  indexOfLeastU ( number, ARRAY_SIZE ) ;

  while ( leastU >= 0 )
    {
    number [leastU]  =  'P' ; // 'P' for Prime

    // mark multiples as Composite ...
    for ( int i = (2 * leastU) ; i < ARRAY_SIZE ; i += leastU )
      number [i]  =  'C' ; // 'C' for Composite

    leastU  =  indexOfLeastU ( number, ARRAY_SIZE ) ;
    } // end while loop
  } // end identifyPrimes function

/*  --------------------------------------------------------
    Function printPrimes prints those array indices whose
    corresponding elements have the value 'P'.
    -------------------------------------------------------- */
void printPrimes ( char number[], int ARRAY_SIZE )
  {
  // print the indices at which a 'P' is stored ...
  cout << "\nThe prime numbers up to 1000 are:\n\n" ;
  for ( int i = 0 ; i < ARRAY_SIZE ; i ++ )
    if ( number[i] == 'P' )
      cout << i << '\t' ;
  cout << endl << endl ;
  } // end printPrimes function

int main ( )
  {
  // declare & initialize constants ...
  const int  MAX_NUMBER  =  1000 ;
  const int  ARRAY_SIZE  =  MAX_NUMBER + 1 ;

  // declare array ...
  char  number [ ARRAY_SIZE ]  =  { '\0' } ;

  initializeNumbers ( number, ARRAY_SIZE ) ;

  identifyPrimes ( number, ARRAY_SIZE ) ;

  printPrimes ( number, ARRAY_SIZE ) ;
  } // end main function 

[nvrmnd]

since you are using strings, it is appropiate to use std::string rather than std::vector.

// basically, you declare a string using :
string myStr( "bbbbbbbbbbbbbb* );
// or
string myStr( 100, ' ' ); // have a string of a size of 100 and fill it w/ spaces

// and access the element using []
myStr[ 10 ] = 'a'; // note that myStr[ 10 ] must be initialized otherwise, it will cause undefined behavior

// you can change the contents of it using the = operator :
myStr = "the quick brown fox jumps over the ..." 

http://www.cplusplus.com/reference/string/string/
http://www.cprogramming.com/tutorial/string.html