How do I properly handle #includes in multi-file programming - c++

Question

First post so take it easy on me :). I don't think I really need to put up any actual code for this, but let me know if I'm wrong. This is for a homework assignment in my college programming class. I am confused as to how to properly use my #include statements. Here is my file structure:
Header Files-->
header.h (Main header file, contains #include for various libraries, declares namespace, and provides my name and class info)
room.h (Blueprint for the room class)
ship.h (Blueprint for the ship class)
Source Files-->
main.cpp (Main Program)
functions.cpp (Functions for the main program)
room.cpp (Functions in the Room class)
ship.cpp (Functions in the Ship class)
Basically, my first instinct was to " #include "header.h" " in room.h, ship.h, main.cpp, and functions.cpp. Then " #include "ship.h" in ship.cpp, and " #include room.h " in room.cpp. However I began getting errors up the wazoo. I was having a similar problem during class but I had my teacher there to sort it out and I'm not exactly sure how we did it, and I also know that tons of errors usually indicates an include error.
Its annoying because I had it working somehow before I added the functions.cpp, but I really want to keep main.cpp pretty clean, so I would rather have functions in a separate file.
What is the best pattern for includes in a situation like this?
EDIT: I'll post my 3 header files
header.h
/*
Author: *********
Class : **********
Assignment : Programming Assignment 2
Description :
This program will construct a ship for the user. It accepts input from a file
containing information on various rooms. It will then check the rooms
validity and add it to the ship if it's valid. Once all of the rooms have been added,
the program will determine if the entire ship is valid and let the user know.
Certification of Authenticity :
I certify that this is entirely my own work, except where I have given
fully - documented references to the work of others.I understand the
definition and consequences of plagiarism and acknowledge that the assessor
of this assignment may, for the purpose of assessing this assignment :
-Reproduce this assignment and provide a copy to another member of
academic staff; and / or
- Communicate a copy of this assignment to a plagiarism checking
service(which may then retain a copy of this assignment on its
database for the purpose of future plagiarism checking)
*/
#ifndef header_h
#define header_h
#include <string>
#include <fstream>
#include <iostream>
#include <sstream>
using namespace std;
#endif
room.h
#ifndef room_h
#define room_h
#include "header.h"
enum RoomType
{
UNKNOWN = -1,
BAY,
LATRINE,
CABIN,
BRIDGE,
NUM_ROOM_TYPES
};
const string ROOM_STRINGS[NUM_ROOM_TYPES] = { "Bay",
"Latrine",
"Cabin",
"Bridge"
};
class Room
{
public:
//default constructor
Room();
//constructor
Room( RoomType type, int width, int breadth, int height );
//destructor
~Room(){};
//accessors
inline RoomType getType() const { return mType; };
inline int getHeight() const { return mHeight; };
inline int getWidth() const { return mWidth; };
inline int getBreadth() const { return mBreadth; };
inline int getVolume() const { return getWidth() * getBreadth() * getHeight(); }; //currently unused
inline string getRoomName(){ return ROOM_STRINGS[mType]; };
string getDescription();
//mutators
void setType(RoomType type) {mType = type; };
void setHeight(int height) {mHeight = height; };
void setWidth(int width) {mWidth = width; };
void setBreadth(int breadth) {mBreadth = breadth; };
private:
//type of room
RoomType mType;
//floor dimensions - in feet
int mWidth;
int mBreadth;
//ceiling height - in feet
int mHeight;
};
#endif
ship.h
#ifndef ship_h
#define ship_h
#include "header.h"
const int MAX_BAY = 4;
const int MAX_LATRINE = 15;
const int MAX_BRIDGE = 1;
const int MAX_CABIN = 25;
const int MIN_BAY = 1;
const int MIN_LATRINE = 1;
const int MIN_BRIDGE = 1;
const int MIN_CABIN = 0;
const int MIN_ROOM_HEIGHT = 7;
const int MIN_ROOM_AREA = 20;
class Ship{
public:
Ship();
bool addRoom(const Room& theRoom);
string getDescription();
//Accessors
int getNumBays(){ return bayTotal; };
int getNumLatrines(){ return latrineTotal; };
int getNumBridges(){ return bridgeTotal; };
int getNumCabins(){ return cabinTotal; };
int getTotalSquareFootage(){ return totalSquareFootage; };
private:
Room Bay[MAX_BAY];
Room Latrine[MAX_LATRINE];
Room Bridge[MAX_BRIDGE];
Room Cabin[MAX_CABIN];
int bayTotal;
int latrineTotal;
int bridgeTotal;
int cabinTotal;
int totalSquareFootage;
bool isShipValid();
void addSquareFootage(float);
};
#endif

Answer 1

What kind of errors? Your issue might be including the same header more than once.
Try adding this to each header:
#ifndef ROOM_H
#define ROOM_H
... code ...
#endif
To be clear the 'ROOM_H' above needs to be unique to each header.

Answer 2

If you use #include "room.h" in different cpp files then you probably get a linker error because this below here is not a type declaration.
const string ROOM_STRINGS[NUM_ROOM_TYPES] = { "Bay",
"Latrine",
"Cabin",
"Bridge"
};
You are creating and allocating a variable with name ROOM_STRINGS. By declaring it in different cpp files you will have multiple copies of the same global variable which is an error. You could replace it with
static const string ROOM_STRINGS[NUM_ROOM_TYPES] = { "Bay",
"Latrine",
"Cabin",
"Bridge"
};
You will still have multiple copies but each cpp file will have its own private copy. A better solution is to move this declaration into the room cpp file together with the code of the getRoomName.
Or you could declare ROOM_STRINGS as extern in the header and then you still need to add the variable allocation in a cpp file.