Thank you 
#include <iostream>
#include <Windows.h>
using namespace std;
int main()
{
int students = 0;
cout << "How much students are you in your class ?" << endl;
cin >> students;
string _students[students];
for (int i = 0; i != students; i++)
{
cout << "Students : " << i << endl;
cin >> _students[i];
}
for (int i = 0; i != students; i++)
{
cout << "Students passwords : \n" << endl;
cout << i << " " << endl;
cout << _students[i];
}
return 0;
}
// Header
#define MAX_PASSWORD_LENGTH 64
// Global pointer
char* passwords;
// Gets the password
char* GetPassword( int id ){
if( passwords ){
return ( char* )( passwords + ( id * MAX_PASSWORD_LENGTH ) );
}
return ""; // No allocated buffer
}
// Sets the password
void SetPassword( int id, char* password ){
strcpy_s( ( char* )( passwords + ( id * MAX_PASSWORD_LENGTH ) ), MAX_PASSWORD_LENGTH, password );
}
// In main
int nStudents = 10; // Number of students ( cin or whatever )
// Allocate the dynamic buffer
passwords = HeapAlloc( GetProcessHeap(), nStudents * MAX_PASSWORD_LENGTH, HEAP_ZERO_MEMORY ); // Allocated dynamic buffer
char tmp[MAX_PASSWORD_LENGTH];
// Save the passwords for each
for( int i=0; i<nStudents; i++ ){
cin >> tmp;
SetPassword( i, tmp );
}
// Output each password
for( int i=0; i<nStudents; i++ ){
cout << " [ " << i << " ]: " << GetPassword( i );
}
// At the end of the program free the buffer
HeapFree( GetProcessHeap, NULL, passwords );