Exception Handling Mechanisms and Debugging Techniques for unordered_map

# 1. Overview and Basic Operations of the unordered_map Container

- **Introduction to the unordered_map Container**
The unordered_map is one of the associative containers in C++ STL, implemented using a hash table that allows for rapid retrieval of elements through key-value pairs. Unlike the map, the unordered_map does not sort its elements, and the time complexity for insertion and access operations is O(1).
- **Declaration and Initialization of the unordered_map Container**
- Creating an empty unordered_map object:

     unordered_map<int, string> myMap;

- Initializing an unordered_map object with initial elements:

     unordered_map<int, string> myMap = {{1, "apple"}, {2, "banana"}};

Continued in part 2...

# 2. Insertion and Access Operations of the unordered_map Container

#### Inserting Elements into the unordered_map Container

##### Using the insert() Method

In the unordered_map container, the insert() method can be used to add new key-value pairs. The insert() method takes a std::pair as a parameter, where the first element is the key, and the second is the value. Below is an example code:

#include <iostream>
#include <unordered_map>

int main() {
     std::unordered_map<int, std::string> umap;

     // Using the insert() method to insert elements
     umap.insert(std::make_pair(1, "apple"));
     umap.insert(std::make_pair(2, "banana"));
     umap.insert(std::make_pair(3, "cherry"));

     return 0;
}

##### Using the emplace() Method

In addition to the insert() method, the emplace() method can also be used to insert elements. The emplace() method takes a parameter pack, which constructs the key-value pair directly and inserts it into the container. An example is shown below:

#include <iostream>
#include <unordered_map>

int main() {
     std::unordered_map<int, std::string> umap;

     // Using the emplace() method to insert elements
     umap.emplace(1, "apple");
     umap.emplace(2, "banana");
     umap.emplace(3, "cherry");

     return 0;
}

#### Accessing Elements in the unordered_map by Key

##### Using the [] Operator

The [] operator can be used to directly access elements in the unordered_map container based on their key. If the key exists, the corresponding value is returned; if it does not, a new key-value pair is inserted. An example is shown below:

#include <iostream>
#include <unordered_map>

int main() {
     std::unordered_map<int, std::string> umap = {{1, "apple"}, {2, "banana"}, {3, "cherry"}};

     // Using the [] operator to access elements
     std::cout << umap[2] << std::endl;   // Outputs "banana"

     return 0;
}

##### Using the at() Method

Another way to access elements is by using the at() method, which takes a key as an argument to retrieve the corresponding value. If the key does not exist, an exception is thrown. An example is shown below:

#include <iostream>
#include <unordered_map>

int main() {
     std::unordered_map<int, std::string> umap = {{1, "apple"}, {2, "banana"}, {3, "cherry"}};

     // Using the at() method to access elements
     std::cout << umap.at(3) << std::endl;   // Outputs "cherry"

     return 0;
}

##### Methods to Check for Element Existence

To determine whether a key-value pair exists in the unordered_map, the count() method or the find() method can be used. The count() method returns the number of occurrences of the s