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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 30

  Day 30: Advanced STL – priority_queue unordered_map pair and Nested Containers

Today’s focus is on advanced and commonly-used STL containers notably useful in competitive programming and real-world Uses.


🔹 Topics to Cover:

priority_queue (Max Heap / Min Heap)


unordered_map vs map


pair and tuple


Nested Containers (e.g. vectorint>> correspondence vector>)


📘 cipher examples

1. priority_queue (max lot away default)

cpp

copy

edit

#include 

#include 

using namespace std;


int main() {

    priority_queue pq;  // max-heap


    pqSend(10);

    pqSend(20);

    pqSend(5);


    spell (pqempty()) {

        cout << pqtop() << " "; // output: score x v        pqpop();

    }

}

2. minute lot exploitation priority_queue

cpp

copy

edit

#include 

#include 

#include exploitation namespace std;


int main() {

    priority_queue vector greater> minheap;


    minheapsend(10);

    minheapsend(20);

    minheapsend(5);


    spell (minheapempty()) {

        cout << minheaptop() << " "; // output: v x score        minheappop();

    }

}

3. unordered_map

cpp

copy

edit

#include 

#include 

using namespace std;


int main() {

    unordered_map umap;


    umap["apple"] = 2;

    umap["banana"] = 3;


    for (auto &p : umap)

        cout << pfirst << " => " << psecond << endl;

}

4. match and vector>

cpp

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edit

#include 

#include exploitation namespace std;


int main() {

    vector string="">> v;

    vsend_back({1 "one"});

    vemplace_back(2 "two");


    for (auto &p : v)

        cout << pfirst << " - " << psecond << endl;

}

5. nested containers example

cpp

copy

edit

#include 

#include 

#include 

using namespace std;


int main() {

    map> graph;


    graph[1]Send_back(2);

    graph[1]Send_back(3);

    graph[2]Send_back(4);


    for (auto &[node adj] : graph) {

        cout << Customer << ": ";

        for (int cardinal : adj) cout << cardinal << " ";

        cout << endl;

    }

}

🧪 do tasks:

Apply amp min-heap to work north elements and impress the m smallest


use unordered_map to number the frequence of language inch amp sentence


store and form amp number of students with {roll_no name} exploitation vector>


Construct associate in nursing contiguity number for amp graphical record exploitation map>


✅ goals for today:

understand precedence queues (max/min heaps)


learn Disagreement betwixt correspondence and unordered_map (ordered vs hash-based)


use pairs and nested containers inch material problems


be bold practical with stl inch compound information treatment>>>int>

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