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CPP (for CP)

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CPP (for CP)

  • Basic syntax and prior C knowledge is assumed

Tips

include bits/stdc++.h can save time including specific header files.

Basic data types

  • data types (int, char, float, double, bool)
  • long int and long long int
  • Size of data types:
#include <iostream>

int main() {
    int a;
    long int b;
    long long int c;
    std::cout << sizeof(a) << std::endl;
    std::cout << sizeof(b) << std::endl;
    std::cout << sizeof(c) << std::endl;
}
  • std::string for working with strings in cpp gives trivial features like concat (+), comparison (==) and, size() etc.
    • std::getline(istream, str) can be used to get a single line input
  • Use arrays for storing collection of items of same data type.
    • Array size is limited.
    • For CP, local array size shouldn't be more than 105 ~int arr[1e5].

Ranges (rough estimation)

  • -109 < int < 109
  • -1012 < long int < 1012
  • -1018 < long long int < 1018
  • header file climits has accurate declared limits
  • sizeof double is higher than long int but it's not used where precise calculation is required.
#include <iostream>
#include <climits>

int main() {
    std::cout << INT_MIN << " < int < " << INT_MAX << std::endl;
}

Calculation precedence (increasing -> decreasing)

Types lower in this list will be converted to higher data types in expressions and outputs.

  • double
  • float
  • long long int
  • long int
  • int
  • char
#include <iostream>

int main() {
    std::cout << 7 / 2 << std::endl; // outputs int
    std::cout << 7 / 2.0 << std::endl; // outputs float
    std::cout << 'a' + 1 << std::endl; // outputs int (ascii values)
}

Operator precedence and associativity

Category Operator Associativity
Postfix () [] -> . ++ - - Left to right
Unary + - ! ~ ++ - - (type)* & sizeof Right to left
Multiplicative * / % Left to right
Additive + - Left to right
Shift << >> Left to right
Relational < <= > >= Left to right
Equality = ! Left to right
Bitwise AND & Left to right
Bitwise XOR ^ Left to right
Bitwise OR | Left to right
Logical AND && Left to right
Logical OR || Left to right
Conditional ?: Right to left
Assignment = += -= *= /= %= >>= <<= &= ^= |= Right to left
Comma , Left to right

CPP References

References can be used to ignore variable copying when calling functions. This does not require any use of pointers.

Example: 

#include <iostream>

// swap takes in references a and b
void swap(int &a, int &b) {
    int temp = a;
    a = b;
    b = temp;
}

int main() {
    int a = 4, b = 3;
    std::cout << a << " " << b << std::endl;
    // this utility function is already declared in <algorithm> header file
    swap(a,b);
    std::cout << a << " " << b << std::endl;
}

Short long long double

#include <iostream>
#include <climits>

using namespace std;

int main () {
    cout << sizeof(int) << endl;
    cout << sizeof(char) << endl;
    cout << sizeof(float) << endl;
    cout << sizeof(double) << endl;

    short a = 3;
    long int b = 69;
    long long int c = 69;
    long double d = 2.0;

    cout << a << endl;
    cout << sizeof(a) << endl;
    cout << sizeof(b) << endl;
    cout << sizeof(c) << endl;
    cout << sizeof(d) << endl;
}

Author: Siddhant Kumar