C++ Tutorial 2
I continue teaching C++ through problem solving. In this video I cover conditional operators, logical operators, if, else, arrays, vectors, converting strings into vectors, string stream, while loops, for loops and more. I’ll also present 2 problems for you to solve, which I’ll then provide the answer to.
I think learning through doing is the best and the problems will keep getting more complex. The code follows the video below to help.
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Transcript / Cheat Sheet
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// ----- CONDITIONAL OPERATORS ----- // Conditional operators help you to perform // different actions depending on conditions // ==, !=, <, >, <=, >= // ----- LOGICAL OPERATORS ----- // Logical operators allow you to combine conditions // && : If both are true it returns true // || : If either are true it returns true // ! : Converts true into false and vice versa // ----- EXAMPLE : IS A BIRTHDAY IMPORTANT ----- // 1 - 18, 21, 50, > 65 : Important // All others are not important std::string sAge = "0"; std::cout << "Enter your age : "; getline(std::cin, sAge); int nAge = std::stoi(sAge); // if and else is used to execute different code // depending on conditions if ((nAge >= 1) && (nAge <= 18)){ std::cout << "Important Birthday\n"; } else if ((nAge == 21) || (nAge == 50)) { std::cout << "Important Birthday\n"; } else if (nAge >= 65){ std::cout << "Important Birthday\n"; } else { std::cout << "Not an Important Birthday\n"; } // ----- END EXAMPLE : IS A BIRTHDAY IMPORTANT —— // ----- PROBLEM : DETERMINE SCHOOL GRADE ----- // If age 5 "Go to Kindergarten" // Ages 6 through 17 go to grades 1 through 12 // If age > 17 "Go to college" // Enter age : 2 // Too young for school // Enter age : 8 // Go to grade 3 // Try to do with 15 or less lines of code std::string sAge = "0"; int nGrade = 0; std::cout << "Enter age : "; getline(std::cin, sAge); int nAge = std::stoi(sAge); if (nAge < 5) std::cout << "To young for school\n"; else if (nAge == 5) std::cout << "Go to Kindergarten\n"; else if ((nAge > 5) && (nAge <= 17)){ nGrade = nAge - 5; std::cout << "Go to grade " << nGrade << "\n"; } else std::cout << "Go to college\n"; // ----- END PROBLEM : DETERMINE SCHOOL GRADE ----- // ---------- C++ Tutorial Example 4 ————— #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <sstream> int main() { // An array is a collection of data of the same type // Declare an array of ints with the value of 1 // Once the size is defined it can't change int arrnNums[10] = {1}; // Leave out the array length int arrnNums2[] = {1,2,3}; // Create an array and assign some values int arrnNums3[5] = {8, 9}; // Access array values using indexes starting with 0 std::cout << "1st Value : " << arrnNums3[0] << "\n"; // Change a value arrnNums3[0] = 7; std::cout << "1st Value : " << arrnNums3[0] << "\n"; // Get array size by getting the number of bytes // set aside for the array and then divide by the size // of the 1st element std::cout << "Array size : " << sizeof(arrnNums3) / sizeof(*arrnNums3) << "\n"; // A multidimensional array is like a spreadsheet // If you think of each as layers that contain columns // 1st Number : Which layer // 2nd Number : Which column // 3rd Number : Which row int arrnNums4[2][2][2] = {{{1,2}, {3,4}}, {{5,6}, {7,8}}}; std::cout << arrnNums4[1][1][1] << "\n"; // Use vectors when you don't know how big your // arrays may be // Create a vector with 2 spaces to start std::vector<int> vecnRandNums (2); // Add values vecnRandNums[0] = 10; vecnRandNums[1] = 20; // Add another value to the vector vecnRandNums.push_back(30); // Get size of vector std::cout << "Vector Size : " << vecnRandNums.size() << "\n"; // Get last value std::cout << "Last Index : " << vecnRandNums[vecnRandNums.size() - 1] << "\n"; // Convert a string into an array std::string sSentence = "This is a random string"; // Create a vector std::vector<std::string> vecsWords; // A stringstream object receives strings separated // by a space and then spits them out 1 by 1 std::stringstream ss(sSentence); // Will temporarily hold each word in the string std::string sIndivStr; // Defines what separates the words char cSpace = ' '; // While there are more words to extract keep // executing // getline takes strings from a stream of words stored // in the stream and each time it finds a blanks space // it stores the word proceeding the space in sIndivStr while(getline(ss, sIndivStr, cSpace)){ // Put the string into a vector vecsWords.push_back(sIndivStr); } // Cycle through each index in the vector and print // out each word for(int i = 0; i < vecsWords.size(); ++i){ std::cout << vecsWords[i] << "\n"; } return 0; } #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <sstream> #include <limits> int main() { // ----- PROBLEM CALCULATOR ----- // Enter calculation (ex. 5 + 6) : 10 - 6 // 10.0 - 6.0 = 4.0 double dbNum1 = 0, dbNum2 = 0; std::string sCalc = ""; std::vector<std::string> vecsCalc; std::cout << "Enter calculation (ex. 5 + 6): "; getline(std::cin, sCalc); std::stringstream ss(sCalc); std::string sIndivStr; char cSpace = ' '; while(getline(ss, sIndivStr, cSpace)){ vecsCalc.push_back(sIndivStr); } dbNum1 = std::stoi(vecsCalc[0]); dbNum2 = std::stoi(vecsCalc[2]); std::string operation = vecsCalc[1]; if (operation == "+"){ printf("%.1f + %.1f = %.1f\n", dbNum1, dbNum2, (dbNum1 + dbNum2)); } else if (operation == "-"){ printf("%.1f - %.1f = %.1f\n", dbNum1, dbNum2, (dbNum1 - dbNum2)); } else if (operation == "*"){ printf("%.1f * %.1f = %.1f\n", dbNum1, dbNum2, (dbNum1 * dbNum2)); } else if (operation == "/"){ printf("%.1f / %.1f = %.1f\n", dbNum1, dbNum2, (dbNum1 / dbNum2)); } else { std::cout << "Please enter only +, -, *, or /\n"; } // ----- END PROBLEM CALCULATOR ----- return 0; } |
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