C++ Part 5
// ----- 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 -----