C++ Tutorial 5
In this part of my C++ tutorial we’ll cover numerous ways to interact with Strings, numerous common Math functions and we’ll solve a rather complex 2 part problem. The goal of this series is to teach the syntax of the C++ language while actually teaching how to solve problems using C++. Each tutorial includes increasingly more complex problems for you to solve. All of the code and a transcript follows the video below.
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Cheat Sheet / Transcript
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// ----- STRING TUTORIAL ----- #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <numeric> #include <sstream> int main() { // A C character string is an array of characters // with a null character at the end \0 char cString[] = {'A', ' ', 'S', 't', 'r', 'i', 'n', 'g', '\0'}; std::cout << cString << "\n"; // Get array size (null is included) std::cout << "Array Size " << sizeof(cString) << "\n"; // C strings are troublesome because if you forget \0, or // add to much information it can lead your program to crash, // or for your system to crash // You can create a vector of strings std::vector<std::string> strVec(10); // C++ std::string can grow in size and is much safer std::string str("I'm a string"); strVec[0] = str; // You can access characters with an index std::cout << str[0] << "\n"; // You can also use at() std::cout << str.at(0) << "\n"; // Front returns first char and back returns last std::cout << str.front() << " " << str.back() << "\n"; // Get the string length std::cout << "Length : " << str.length() << "\n"; // You can copy a string to another std::string str2(str); strVec[1] = str2; // You can copy after the 1st 4 characters std::string str3(str, 4); strVec[2] = str3; // Repeat a value to make a string std::string str4(5, 'x'); strVec[3] = str4; // Combine strings with append or + strVec[4] = str.append(" and your not"); str += " and your not"; // Append part of a string str.append(str, 34, 37); strVec[5] = str; // Erase characters from a string from an index to another // or the last str.erase(13, str.length() - 1); strVec[6] = str; for(auto y: strVec) std::cout << y << "\n"; // find() returns index where pattern is found // or npos if(str.find("string") != std::string::npos) std::cout << "1st not " << str.find("string") << "\n"; // substr(x, y) returns a substring starting at // index x with a length of y std::cout << "Substr " << str.substr(6,6) << "\n"; // Reverse a string by passing the beginning and end // of a string reverse (str.begin(), str.end()); std::cout << "Reverse " << str << "\n"; // Case conversion transform(str2.begin(), str2.end(), str2.begin(), ::toupper); std::cout << "Upper " << str2 << "\n"; transform(str2.begin(), str2.end(), str2.begin(), ::tolower); std::cout << "Lower " << str2 << "\n"; // You can get the ascii code for a char by saving // the char as an int or with (int) // a - z : 97 - 122 // A - Z : 65 - 90 char aChar = 'Z'; int aInt = aChar; std::cout << "A Code " << (int)'a' << "\n"; // Convert int to string std::string strNum = std::to_string(1+2); std::cout << "String " << strNum << "\n"; // ----- PROBLEM : SECRET STRING ----- // Receive an uppercase string and hide its meaning // by turning it into ascii codes // Translate it back to the original letters std::string normalStr, secretStr = ""; std::cout << "Enter your string in uppercase : "; std::cin >> normalStr; // Cycle through each character converting // them into ascii codes which are stored in // a string for(char c: normalStr) secretStr += std::to_string((int)c); // secretStr += std::to_string((int)c - 23); std::cout << "Secret : " << secretStr << "\n"; normalStr = ""; // Cycle through numbers in string 2 at a time for(int i = 0; i < secretStr.length(); i += 2){ // Get the 2 digit ascii code std::string sCharCode = ""; sCharCode += secretStr[i]; sCharCode += secretStr[i+1]; // Convert the string into int int nCharCode = std::stoi(sCharCode); // Convert the int into a char char chCharCode = nCharCode; // char chCharCode = nCharCode + 23; // Store the char in normalStr normalStr += chCharCode; } std::cout << "Original : " << normalStr << "\n"; // ----- END OF PROBLEM : SECRET STRING ----- // ----- BONUS PROBLEM ----- // Allow the user to enter upper and lowercase // letters by subtracting and adding 1 value // ----- END OF BONUS PROBLEM ----- return 0; } // ----- END OF STRING TUTORIAL —— // ----- MATH FUNCTIONS ----- // C++ has numerous math functions // http://en.cppreference.com/w/cpp/numeric/math // Needed for math functions #include <cmath> int main() { std::cout << "abs(-10) = " << std::abs(-10) << "\n"; std::cout << "max(5,4) = " << std::max(5,4) << "\n"; std::cout << "min(5,4) = " << std::min(5,4) << "\n"; std::cout << "fmax(5.3,4.3) = " << std::fmax(5.3,4.3) << "\n"; std::cout << "fmin(5.3,4.3) = " << std::fmin(5.3,4.3) << "\n"; // e ^ x std::cout << "exp(1) = " << std::exp(1) << "\n"; // 2 ^ x std::cout << "exp2(1) = " << std::exp2(1) << "\n"; // e * e * e ~= 20 so log(20.079) ~= 3 std::cout << "log(20.079) = " << std::log(20.079) << "\n"; // 10 * 10 * 10 = 1000, so log10(1000) = 3 std::cout << "log10(1000) = " << std::log10(1000) << "\n"; // 2 * 2 * 2 = 8 std::cout << "log2(8) = " << std::log2(8) << "\n"; // 2 ^ 3 std::cout << "pow(2,3) = " << std::pow(2,3) << "\n"; // Returns what times itself equals the provided value std::cout << "sqrt(100) = " << std::sqrt(100) << "\n"; // What cubed equals the provided std::cout << "cbrt(1000) = " << std::cbrt(1000) << "\n"; // Hypotenuse : SQRT(A^2 + B^2) std::cout << "hypot(2,3) = " << std::hypot(2,3) << "\n"; std::cout << "ceil(10.45) = " << std::ceil(10.45) << "\n"; std::cout << "floor(10.45) = " << std::floor(10.45) << "\n"; std::cout << "round(10.45) = " << std::round(10.45) << "\n"; // Also sin, cos, tan, asin, acos, atan, atan2, // sinh, cosh, tanh, asinh, acosh, atanh return 0; } // ----- END OF MATH FUNCTIONS ----- |
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