Add content of day 08 #504

docs/day-08/_category_.json

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+{
+    "label": "Day 08",
+    "position": 8,
+    "link": {
+      "type": "generated-index"
+    }
+  }

docs/day-08/strings.md

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+1. Introduction to Strings in C++
+
+A string is a sequence of characters. In C++, there are two main ways to work with strings:
+
+    1. C-style strings (character arrays)
+    2. The C++ string class
+
+
+2. C-style Strings
+
+C-style strings are inherited from the C language. They are essentially arrays of characters ending with a null character '\0'.
+Example:
+
+cppCopychar str[] = "Hello";  // Equivalent to {'H','e','l','l','o','\0'}
+Pros:
+
+Low-level control
+Compatibility with C code
+
+Cons:
+
+Prone to buffer overflow errors
+Limited built-in functionality
+
+
+3. C++ String Class
+
+The C++ string class is part of the Standard Template Library (STL). It's much more powerful and safer to use than C-style strings.
+To use the string class, include the <string> header:
+cppCopy#include <string>
+using namespace std;
+
+string str = "Hello, World!";
+
+4. String Declaration and Initialization
+
+You can declare and initialize strings in several ways:
+cppCopystring s1;               // Empty string
+string s2 = "Hello";     // Initialize with a string literal
+string s3("World");      // Initialize using constructor
+string s4(5, 'A');       // Initialize with 5 'A' characters: "AAAAA"
+string s5 = s2;          // Copy initialization
+
+5. String Operations
+
+a. Concatenation:
+cppCopystring a = "Hello";
+string b = "World";
+string c = a + " " + b;  // c is "Hello World"
+
+b. Appending:
+cppCopystring str = "Hello";
+str += " World";         // str is now "Hello World"
+
+c. Accessing characters:
+cppCopystring str = "Hello";
+char ch = str[0];        // ch is 'H'
+
+d. Length:
+cppCopystring str = "Hello";
+int len = str.length();  // or str.size(); both return 5
+
+e. Substring:
+cppCopystring str = "Hello, World!";
+string sub = str.substr(7, 5);  // sub is "World"
+
+f. Finding:
+cppCopystring str = "Hello, World!";
+size_t pos = str.find("World");  // pos is 7
+
+g. Replacing:
+cppCopystring str = "Hello, World!";
+str.replace(7, 5, "C++");  // str is now "Hello, C++!"
+
+6. String Input/Output
+
+a. Output:
+cppCopystring str = "Hello";
+cout << str << endl;
+
+b. Input:
+cppCopystring name;
+cout << "Enter your name: ";
+cin >> name;  // Reads until whitespace
+
+c. Reading a line:
+cppCopystring line;
+getline(cin, line);  // Reads entire line, including spaces
+
+7. String Comparison
+
+You can compare strings using relational operators:
+cppCopystring s1 = "apple";
+string s2 = "banana";
+if (s1 < s2) {
+    cout << "apple comes before banana" << endl;
+}
+
+8. String Conversion
+
+a. To C-style string:
+cppCopystring str = "Hello";
+const char* cstr = str.c_str(); 
+
+b. Number to string:
+cppCopyint num = 123;
+string str = to_string(num);
+
+c. String to number:
+cppCopystring str = "123";
+int num = stoi(str);  // string to int
+double d = stod(str); // string to double
+
+9. String Iteration
+
+You can iterate through a string using range-based for loop or traditional for loop:
+cppCopystring str = "Hello";
+for (char c : str) {
+    cout << c << " ";
+}
+
+10. String Modifiers
+
+a. Insert:
+cppCopystring str = "Hello";
+str.insert(5, " World");  // str is now "Hello World"
+
+b. Erase:
+cppCopystring str = "Hello World";
+str.erase(5, 6);  // str is now "Hello"
+
+c. Clear:
+cppCopystring str = "Hello";
+str.clear();  // str is now an empty string
+
+11. String Capacity
+
+a. Resize:
+cppCopystring str = "Hello";
+str.resize(10, '!');  // str is now "Hello!!!!!"
+
+b. Capacity:
+cppCopystring str = "Hello";
+cout << str.capacity();  // Prints the current capacity
+
+12. Advanced String Operations
+
+a. Regular expressions (C++11 and later):
+cppCopy#include <regex>
+string str = "Hello, 123";
+regex pattern("\\d+");
+if (regex_search(str, pattern)) {
+    cout << "String contains digits" << endl;
+}
+
+b. String view (C++17):
+cppCopy#include <string_view>
+string_view sv = "Hello, World!";
+cout << sv.substr(0, 5);  // Efficient substring operation