The Standard Template Library (STL) is a set of C++ template classes that provide common data structures and functions like lists, stacks, and arrays. It discusses using maps to find the frequency of numbers in a list, with maps allowing to search in logarithmic time and store elements in sorted order. It also covers sets, vectors, sorting functions, and provides example problems on programming platforms to practice STL.

1. STL (Standard Template
Library)

2. What is STL?
The Standard Template Library (STL) is a set of C++
template classes to provide common programming
data structures and functions such as lists, stacks,
arrays, etc.

3. Question
Find the frequency of all the numbers??
Eg. 1 1 2 2 1 1 3 5 5
1 - 4
2 -2
3 - 1
5 - 2

4. Solutions
1. Brute Force
2. Hashing

5. Problems with this solution
1. Too much memory waste
2. Not able to solve for big numbers

6. MAP to the rescue
● #include <map>
● Key Value store
● Traversing through iterators
● Search in log(n)
● size(), find(),clear

7. Map properties
● Stores in sorted order
● Searching in logn
● Erase in logn

8. Set
● When to use?
● Syntax
● Traversing
● Find function
● Complexities

9. Vector
● Similar to array
● Push_back
● Size

10. Other STL functions
● sort
● next_permutation
● Reverse
● Memset
● __gcd

11. Questions
● https://www.hackerrank.com/challenges/cpp-maps/problem
● https://www.hackerrank.com/challenges/cpp-sets/problem
● https://www.hackerearth.com/problem/algorithm/shikhar-stl/
● https://www.codechef.com/problems/KJCP02
● https://www.codechef.com/problems/CSS2
● https://www.codechef.com/LRNDSA02/problems/NOTALLFL
● https://www.codechef.com/JUNE20B/problems/CHFICRM
● https://www.codechef.com/DEC14/problems/CAPPLE/