C++ STL Introduction

What is the STL?

The Standard Template Library (STL) is a powerful set of ready-to-use C++ template classes and functions. It provides generic containers, algorithms, and iterators.

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

int main() {
    vector<int> nums = {5, 3, 8, 1, 9, 2};

    sort(nums.begin(), nums.end());

    for (int n : nums) cout << n << " ";
    cout << endl;

    auto it = find(nums.begin(), nums.end(), 8);
    if (it != nums.end())
        cout << "Found 8 at position " << (it - nums.begin()) << endl;

    cout << "Count of 3: " << count(nums.begin(), nums.end(), 3) << endl;
    return 0;
}

Output:

1 2 3 5 8 9
Found 8 at position 4
Count of 3: 1

Common STL Algorithms

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

int main() {
    vector<int> v = {7,2,9,1,5,3,8,4,6,10};
    sort(v.begin(), v.end());
    cout << "Min: " << *min_element(v.begin(), v.end()) << endl;
    cout << "Max: " << *max_element(v.begin(), v.end()) << endl;
    cout << "Sum: " << accumulate(v.begin(), v.end(), 0) << endl;
    return 0;
}

Summary

• STL provides containers (vector, map, set), algorithms, and iterators.
• Include <algorithm> for sort, find, count, reverse, etc.
• All algorithms work with iterators: begin() to end().