DSA 100 Days of Learning

 DSA

LANGUAGE OPTED - C++

                      DAY-1                    

1. Check Even and Odd:-

if (num & 1)

 cout << "Odd"; 

else

cout << "Even";

• Even numbers have a least significant bit (LSB) of 0.
• Odd numbers have an LSB of 1.

Example:

• For num = 6:
• Binary of 6 is 0110.
• 6 & 1 results in 0110 & 0001 which equals 0000 (0 in decimal).
• Since the result is 0, the else block executes, indicating that 6 is even

2. Functions in C++ :-

In C++, it's a good practice to define functions before the main() function. However, if you define a function after the main() function, you need to declare it before main().

#include <iostream>

using namespace std;

void printLine(); 

int main() {

    printLine(); // Function call

    return 0;

}

void printLine() {

    cout << "Have a good day!";

}

3. Vector STL in C++ :-

a) Sum of array. Array size declared by user at run-time :-

#include <iostream>

#include <vector>

using namespace std;

// Function to print the elements of the vector

void print(const vector<int>& x) {

    cout << "The array is: ";

    for (auto it : x) {

        cout << it << " ";

    }

    cout << endl;

}

int main() {

    vector<int> a;

    int sum = 0, n;

    // Input the size of the vector

    cout << "Enter the size of the array/VECTOR: ";

    cin >> n;

    // Input the elements of the vector

    cout << "Enter the elements: ";

    for (int i = 0; i < n; ++i) {

        int x;

        cin >> x;

        a.push_back(x);

    }

    // Print the elements of the vector

    print(a);

    // Calculate the sum of the elements

    for (const auto& val : a) {

        sum += val;

    }

    // Output the sum of the elements

    cout << "The sum of the array is: " << sum << endl;

    a.clear();

    return 0;

}

Pass by Reference:  void print(const vector<int>& x) instead of void print(vector<int>x) 

• When you pass the vector by reference, no copy is made.
• Instead, the function receives a reference to the original vector.
• Adding const ensures that the function does not modify the vector, providing both safety and clarity.
• This is much more efficient, as it avoids the overhead of copying the entire vector