Basic Data Types

#include <iostream>

using namespace std;

int main() {

int a;
long b;
char c;
float d;
double e;
e;
   cin >>a>>b>>c>>d>>e;
   cout << fixed;
   cout << a<<'\n';
   cout << b<<'\n';
   cout << c<<'\n';
   cout << d<<'\n';
   cout << e<<'\n';
 return 0;
}

Conditional Statements

#include <bits/stdc++.h>

using namespace std;



int main()
{
    string a[]={"Greater than 9","one","two","three","four","five","six","seven","eight","nine"};

    int n;
    cin >> n;
    if(n>9){
        cout << a[0];
    }
else {
cout << a[n];
}

    return 0;
}

For Loop

#include <bits/stdc++.h>

using namespace std;

int main() {
  string a[] = {"one", "two",   "three", "four", "five",
                "six", "seven", "eight", "nine"};

  int n, c;
  cin >> n >> c;
  for (; n <= c; n++) {
    if (n > 9 && c > 9 && n % 2 == 0) {
      cout << "even" << endl;
    } else if (n > 9 && c > 9 && n % 2 != 0) {
      cout << "odd" << endl;
    } else {
      cout << a[n - 1] << endl;
    }
  }

  return 0;
}

Functions

#include <iostream>
#include <cstdio>
using namespace std;

int main (){
    int i;
    int a[4];
    for(i=0;i<4;i++){
    cin >> a[i];
    }
  int  max=a[0];
    for(i=0;i<4;i++){
if (a[i]>max){
    max=a[i];
}

    }
cout<<max;






    return 0; }

Pointer

# include <iostream>
using namespace std;
int main(){
int a,b,c,d;
cin >>a>>b;
c=a+b;
if (a>=b){
d=a-b;}
else{
    d=b-a;
}
cout<<c<<endl<<d;
return 0;
}

Arrays Introduction

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <vector>
using namespace std;

int main() {
  int i, n;
  cin >> n;
  int a[n];
  for (i = 0; i <= n - 1; i++) {
    cin >> a[i];
  }
  for (i = n - 1; i >= 0; i--) {

    cout << a[i] << ' ';
  }

  return 0;
}

Variable Sized Arrays

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
   int n,q;
cin >> n >> q;
vector< vector<int> > a(n);

// input each array
for (int i=0;i<n;i++) {
    int k;
    cin >> k;

    for (int j=0;j<k;j++) {
        int data;
        cin >> data;
        a[i].push_back(data);
    }
}

// do the queries
for (int i=0;i<q;i++) {
    int x,y;
    cin >> x >> y;
    cout << a[x][y] << endl;
}
    return 0;
}

StringStream

#include <iostream>
#include <string>

using namespace std;

int main() {
  string s;
  cin >> s;
  for (size_t f = 0; (f = s.find(",", f)) != string::npos;
       s.replace(f, 1, "\n"))
    ;
  cout << s << endl;
  return 0;
}

Strings

#include <bits/stdc++.h>

using namespace std;

int main() {
  string a, b;
  cin >> a >> b;

  cout << a.length() << ' ' << b.length() << endl;

  cout << a + b << endl;

  swap(a[0], b[0]);
  cout << a << ' ' << b << endl;

  return 0;
}

Structs

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

struct Student { int age; string first_name; string last_name; int standard; };

int main() { Student st; std::string str1; std::string str2; cin >> st.age; cin>>str1; cin>>str2; cin>> st.standard; st.first_name=str1.substr(0,50); st.last_name=str2.substr(0,50);

cout << st.age << " " << st.first_name << " " << st.last_name << " " << st.standard;

return 0;
}

Class

#include <iostream>
#include <sstream>
using namespace std;




class Student {
private:
int age;
string first_name;
string last_name;
int standard;

public:

void set_age (int a){
    age=a;
}
void set_first_name (string a){
    first_name=a;
}
void set_last_name (string b){
    last_name=b;
}
void set_standard (int c){
    standard=c;
}

int get_age(){
    return age;
}
string get_first_name(){
    return first_name;
}
string get_last_name(){
    return last_name;
}
int get_standard(){
    return standard;
}

string to_String(){
  return to_string(age) + "," + first_name + "," + last_name + "," +
         to_string(standard);
}

};

int main() {
    int age, standard;
    string first_name, last_name;

    cin >> age >> first_name >> last_name >> standard;

    Student st;
    st.set_age(age);
    st.set_standard(standard);
    st.set_first_name(first_name);
    st.set_last_name(last_name);

    cout << st.get_age() << "\n";
    cout << st.get_last_name() << ", " << st.get_first_name() << "\n";
    cout << st.get_standard() << "\n";
    cout << "\n";
    cout << st.to_String();

    return 0;
}

Classes and Objects


class Student{
    int scores[5];
    public:
    void input(){
        for(int i=0; i<5; i++){
            cin >> scores[i];
        }
    }
    int calculateTotalScore(){
        int total = 0;
        for(int i=0; i<5; i++){
            total += scores[i];
        }
        return total;
    }
};


Box It!

class Box{
    private:
    int l, b, h;
    public:
    Box(){
        l = 0;
        b = 0;
        h = 0;
    }
    Box(int length, int breadth, int height){
        l = length;
        b = breadth;
        h = height;
    }
    Box(const Box& B){
        l = B.l;
        b = B.b;
        h = B.h;
    }

    int getLenght(){
        return l;
    }
    int getBreadth(){
        return b;
    }
    int getHeight(){
        return h;
    }
    long long CalculateVolume(){
        return (long long)l*b*h;
    }

    friend bool operator < ( Box&A,Box& B){
        if( (A.l < B.l) || ((A.b < B.b) && (A.l == B.l)) || ((A.h < B.h) && (A.l == B.l) && (A.b == B.b)) ){
            return true;
        }else{
            return false;
        }
    };

    friend ostream& operator<< (ostream& output, const Box& B){
        output << B.l << " " << B.b << " " << B.h;
        return output;
    }
};

Vector-Sort

#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>

int main() {
    std::vector<int> v;
    int n;
    std::cin >> n;

    std::copy_n(std::istream_iterator<int>(std::cin), n, std::back_insert_iterator<std::vector<int>>(v));
    std::sort(v.begin(), v.end());
    std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));

    return 0;
}

Vector-Erase

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
   int n;
cin >> n;
vector <int> v;
int a;
for(int i=0;i<n;i++){
   cin >> a;
   v.push_back(a);
}
int k;
cin >> k;
v.erase(v.begin()+k-1);
int l,m;
cin >> l >> m;
v.erase(v.begin()+l-1,v.begin()+m-1);
cout << v.size()<<endl;
for(int i=0; i<v.size();i++){
    cout << v[i] << " ";
}
return 0;
}

Lower Bound-STL

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
   /* Enter your code here. Read input from STDIN. Print output to STDOUT */
   int m, num;
   cin >> m;
   vector<int> v;
   for (int i=0; i<m; i++){
       cin >> num;
       v.push_back(num);
   }
   int n, val;
   cin >> n;
   for (int i=0; i<n; i++){
       cin >> val;
       vector<int>::iterator low = lower_bound(v.begin(), v.end(), val);
       if (v[low - v.begin()] == val)
           cout << "Yes " << (low - v.begin()+1) << endl;
       else
           cout << "No " << (low - v.begin()+1) << endl;
   }
   return 0;
}

Sets-STL

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <algorithm>
using namespace std;


int main() {
int iCount;
set<int> ss;
cin >> iCount;
for (int i=0; i<iCount; ++i){
    int type, query;
    cin >> type >> query;
    switch (type){
        case 1:
            ss.insert(query);
            break;
        case 2:
            ss.erase(query);
            break;
        case 3:
            cout << (ss.find(query) == ss.end() ? "No" : "Yes") << endl;
            break;
    }
}
return 0;
}

Maps-STL

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <set>
#include <map>
#include <algorithm>
using namespace std;


int main() {
    int q, type; cin >> q;
    map<string,int> clas; string name;
    for (int i(0), mark; i<q; ++i)
    {
        cin >> type >> name;
        if (type == 1){
            cin >> mark;
            clas[name] += mark;
        }
        else if (type == 2)
            clas.erase(name);
        else
            cout << clas[name] << "\n";
    }
    return 0;
}

Print Pretty



		   cout << hex << showbase << nouppercase<<left;
    cout << (long long)A << endl;


    cout << setw(15) << showpos << setfill('_') << setprecision(2)<<fixed<<right;
    cout << B << endl;


    cout << scientific << setw(15) << setprecision(9) << uppercase<<noshowpos;
    cout << C << endl;

Inheritance Introduction

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


class Triangle{
    public:
       void triangle(){
           cout<<"I am a triangle\n";
       }
};
class Isosceles : public Triangle{
    public:
       void isosceles(){
          cout<<"I am an isosceles triangle\n";
       }

       void description(){
          cout<<"In an isosceles triangle two sides are equal\n";
       }
};
int main(){
    Isosceles isc;
    isc.isosceles();
     isc.description();
    isc.triangle();
    return 0;
}

Rectangle Area


class Rectangle
{
public:
    Rectangle() = default;
    virtual void display() const { std::cout << _width << " " << _height << std::endl; }
    int area() const { return _width * _height; }
protected:
    int _width = 0;
    int _height = 0;
};

class RectangleArea : public Rectangle
{
public:
    RectangleArea() = default;
    virtual void display() const override { std::cout << area() << std::endl; }
    void read_input() { std::cin >> _width >> _height; }
};

Multi Level Inheritance

#include <iostream>
#include <memory>

class Shape
{
public:
    virtual const void triangle()const = 0;
    virtual ~Shape(){   }
};

class Triangle: public Shape
{
public:
    virtual const void triangle()const override
    { std::cout<<"I am a triangle\n";   }
    virtual ~Triangle(){    }
};

class Isosceles : public Triangle
{
public:
    virtual const void triangle()const override
    {   std::cout<<"I am an isosceles triangle\n";  }
    virtual ~Isosceles(){   }
};
class Equilateral: public Isosceles
{
public:
    virtual const void triangle()const override
    {   std::cout<<"I am an equilateral triangle\n";  }
    virtual ~Equilateral(){   }
};

int main()
{
    std::shared_ptr<Shape> obj[3];

    obj[0] = std::make_shared<Equilateral>();
    obj[1] = std::make_shared<Isosceles>();
    obj[2] = std::make_shared<Triangle>();

    for(auto it: obj)
        it->triangle();
    return 0;
}


C++ Class Templates


template <class T> class AddElements {
    public:
        T element;
        AddElements(T i) {element = i;}
        T add(T i) {return element+i;}
    private:

};
template <> class AddElements <string> {
    public:
        string element;
        AddElements(string i) {element = i;}
        string concatenate(string element2) {return element+element2;}
    private:

};

Overload Operators


ostream &operator<<(ostream &os, const Complex &c) {
  return os << c.a << (c.b > 0 ? '+' : '-') << 'i' << c.b;
}

Complex operator+(const Complex &a, const Complex &b) {
  return {a.a + b.a, a.b + b.b};
}

//Overload operators + and << for the class complex
//+ should add two complex numbers as (a+ib) + (c+id) = (a+c) + i(b+d)
//<< should print a complex number in the format "a+ib"