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C++ Day 39

  C++ Day 39 STL Containers (Deep Understanding & Real Usage) Till now, you already know arrays, vectors, loops, and STL algorithms. Today, we go one step deeper and understand STL containers , which are the backbone of modern C++ programming. In real projects and competitive coding, choice of container matters a lot. 1. What are STL Containers? STL containers are data structures provided by C++ to store data efficiently. They handle: memory management resizing element access performance optimization You focus on logic , not memory handling. 2. Categories of STL Containers STL containers are mainly divided into: Sequence Containers Associative Containers Unordered Containers Container Adapters 3. Sequence Containers These store data in sequence . 3.1 Vector Most used container in C++. vector< int > v; Key Features: Dynamic size Contiguous memory Fast random access Slower insertion in middle Example: v. push_...
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C++ Day 16

 ✅ Task:

Read a text, and turn it into a number. If this does not work, say "Bad String."


🧠 Idea:

Use error checks (try-catch) in C++ to deal with errors in turning text to a number.


📥 Input:

Just one text S.


📤 Output:

Show the number if the text is okay.


If not, say "Bad String".


✅ Good Input:

yaml

Copy

Edit

1234

✅ Good Output:

yaml

Copy

Edit

1234

❌ Bad Input:

nginx

Copy

Edit

abc

❌ Bad Output:

arduino

Copy

Edit

Bad String

✅ C++ Way to do it:

cpp

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#include <iostream>

#include <string>

using namespace std;


int main() {

    string S;

    cin >> S;

    try {

        int number = stoi(S);  // std::stoi throws if it can't change the text

        cout << number << endl;

    } catch (...) {

        cout << "Bad String" << endl;

    }

    return 0;

}

📝 Tips:

stoi() gives invalid_argument if the text can't be turned.


You can catch (exception &e) or catch (...) to get all errors.


This helps you learn how to deal with bad inputs and error checks in C++.

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