Hackerrank Box It

Question

I decided to solve the Box It! challenge in Hackerrank to improve my C++ knowledge as I'm still new to the language.

Design a class named Box whose dimensions are integers and private to the class. The dimensions are labeled: length \$l\$ , breadth \$b\$ , and height \$h\$.

The default constructor of the class should initialise \$l\$ ,\$b\$ ,\$h\$ and to length, breadth and height .

The parameterized constructor Box(int length, int breadth, int height) should initialize Box's \$l\$ , \$b\$ and \$h\$ to length, breadth and height.

The copy constructor Box(Box B) should set \$l\$ , \$b\$ and \$h\$ to \$B\$ 's \$l\$ , \$b\$ and \$h\$ respectively.

Apart from the above, the class should have \4ドル\$ functions:

• int getLength() - Return box's length
• int getBreadth() - Return box's breadth
• int getHeight() - Return box's height
• long long CalculateVolume() - Return the volume of the box

Overload the operator for the class Box. Box \$A \leq \$ Box \$B\$ if:

• \$ A.l \leq B.l\$
• \$ A.b \leq B.b\$ and \$ A.l == B.l\$
• \$ A.h \leq B.h\$ and \$ A.b == B.b\$ and \$ A.l == B.l\$

Overload operator \$<<\$ for the class Box().

If \$B\$ is an object of class Box:

\$cout << B\$ should print \$ B.l, B.b \$ and \$B.h\$ on a single line separated by spaces.

Constraints

\0ドル \leq l,b,h \leq 10^5\$ Two boxes being compared using the \$<\$ operator will not have all three dimensions equal.

Here is my code

#include<bits/stdc++.h> 
using namespace std;
class Box{
 int length, breadth, height;
 public:
 Box (){
 length =0;
 breadth = 0;
 height =0;
 }
 Box (int l, int b, int h)
 {
 length =l;
 breadth = b;
 height = h;
 }
 Box(const Box& b){
 length = b.length;
 breadth = b.breadth;
 height = b.height;
 }
 int getLength(){
 return length;
 }
 int getBreadth (){
 return breadth;
 }
 int getHeight(){
 return height;
 }
 long long CalculateVolume(){
 return (long long) length * breadth * height;
 }
 bool operator<(Box& b){
 if(this->length <= b.length || this->breadth <= b.breadth && this->length == b.length || 
 this->height <= b.height && this->length == b.length && this->breadth == b.breadth)
 {
 return true;
 }
 return false;
 }
 friend ostream& operator<<(ostream &out, const Box &B);
};
 ostream& operator<<(ostream &out, const Box &B){
 out<< B.length<<" "<< B.breadth<< " " << B.height;
 return out;
 }
void check2()
{
 int n;
 cin>>n;
 Box temp;
 for(int i=0;i<n;i++)
 {
 int type;
 cin>>type;
 if(type ==1)
 {
 cout<<temp<<endl;
 }
 if(type == 2)
 {
 int l,b,h;
 cin>>l>>b>>h;
 Box NewBox(l,b,h);
 temp=NewBox;
 cout<<temp<<endl;
 }
 if(type==3)
 {
 int l,b,h;
 cin>>l>>b>>h;
 Box NewBox(l,b,h);
 if(NewBox<temp)
 {
 cout<<"Lesser\n";
 }
 else
 {
 cout<<"Greater\n";
 }
 }
 if(type==4)
 {
 cout<<temp.CalculateVolume()<<endl;
 }
 if(type==5)
 {
 Box NewBox(temp);
 cout<<NewBox<<endl;
 }
 }
}
int main()
{
 check2();
}

Final thoughts

• I now I shouldn't be using this line of code using namespace std; as recommended in other reviews but Hackerrank had this pre-defined and I couldn't change it. The Check2() and main() were also predefined as well.

• Was the use of friend method an overkill?

• Did I override the operators << and < correctly?
• How can I improve this code?

• user33306: Just an fyi, you can change any of the code that Hackerrank supplies. As long as the code will compile, it will accept it.
• fernando.reyes: You need parenthesis on your operator< otherwise the comparisons are made serially
• Tolani: @tinstaafl the code is in a locked editor and I'm only meant to write a class that will be called by the locked editor
• user33306: OK. I also noticed the the < operator code only tests < but the description uses <=.
• Tolani: I must have changed it whilst copying the code to an editor . Good Spot on . I will make amends

Answer 1

• The problem statement defines the less than condition differently.

• I recommend to use tuple<int, int, int> for box dimensions. The default operator< for tuples does exactly what the problem statement asks for.

• The

  if (condition)
  {
   return true;
  }
  return false;
  

  is a long way to say

  return condition;
  

• this-> is just a noise. You may safely refer to this->length as length.

• An indentation for operator<< is confusing, but I assume it a copy-paste error.

• #include <bits/stdc++.h> is always wrong.

Answer 2

It's strange to use a signed type for length, but that appears to be imposed on you by the problem statement, so blame a poor specification for that.

Despite the letters std, <bits/stdc++.h> is not a standard header, so you have a portability bug. Even where it exists, it brings in far more than you need, so get used to including just the headers you need.

Avoid using namespace std; - that deprives you of the benefits of namespacing. If you really can't type std:: where needed, then import just the names you need into the smallest reasonable scope:

void check2()
{
 using std::cin;
 using std::cout;
 using std::endl;
 //...
}

Prefer to use initialisers to set members - a good compiler (e.g. g++ -Weffc++) can warn when you forget one:

Box()
 : Box{0, 0, 0}
{
}
Box(int length, int breadth, int height)
 : length{length},
 breadth{breadth},
 height{height}
{
}

We can omit the Box(const Box&) constructor, as the compiler-generated one is identical.

Many methods are missing const qualifiers:

int getLength() const;
int getBreadth () const;
int getHeight() const;
long long CalculateVolume() const;
bool operator<(const Box& b) const;

check2 is a completely meaningless name; choose a name that demonstrates its purpose. Similarly, what does temp mean to the reader?

When reading input, always check the state of the stream afterwards:

if (!(std::cin >> l >> b >> h)) {
 // deal with input error here
}