c_cpp CPP - 教程007 - 更多练习题

Posted 2021-05-14

// ----- 7. PROBLEM CAESAR CIPHER -----
std::string CaesarCipher(std::string theString, int key, 
        bool encrypt);

int main() {
    
    std::string theString = "Make me secret";
    
    std::string encryptedStr = CaesarCipher(theString, 
            5, true);
    
    std::string decryptedString = CaesarCipher(encryptedStr, 
            5, false);
    
    std::cout << "Encrypted " << encryptedStr << "\n";
    
    std::cout << "Decrypted " << decryptedString << "\n";
    
    return 0;
    
}

std::string CaesarCipher(std::string theString, int key, 
        bool encrypt){
    std::string returnString = "";
    int charCode = 0;
    char letter;
    
    // The key will shift and unshift character codes
    if(encrypt) key = key * -1;
    
    // Cycle through each character
    for(char& c : theString) {
        
        // Check if it's a letter and if not don't chage it
        if(isalpha(c)){
            
            // Convert from char to int and shift the char code
            charCode = (int)c;
            charCode += key;
            
            // If uppercase check if the new character code >
            // char code for Z, or < char code for A
            // If so shift the character code so that its value
            // wraps back into the letter character codes
            if(isupper(c)){
                
                if(charCode > (int)'Z'){
                    charCode -= 26;
                } else if(charCode < (int)'A'){
                    charCode += 26;
                }
                
            } else {
                
                // Do the same for lowercase letters
                if(charCode > (int)'z'){
                    charCode -= 26;
                } else if(charCode < (int)'a'){
                    charCode += 26;
                }
                
            }
            
            // Convert from int to char and add the returning string
            letter = charCode;
            returnString += letter;
            
        } else {
            letter = c;
            returnString += c;
            std::cout << c << "\n";
        }
        
    }
    
    return returnString;
}

// ----- END PROBLEM CAESAR CIPHER -----

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <numeric>
#include <sstream>

// ----- 1. PROBLEM : SOLVE FOR X -----

std::vector<std::string> StringToVector(std::string theString, 
        char separator);
        
void SolveForX(std::string equation);

int main() {
    
    // Make a function that receives an algebraic 
    // equation like x + 4 = 9 and solve for x
    // x will always be the 1st value received 
    // and you only will deal with addition
    std::cout << "Enter an equation to solve ";
    std::string equation = "";
    getline(std::cin, equation);
    SolveForX(equation);
    
    return 0;
    
}

std::vector<std::string> StringToVector(std::string theString, 
        char separator){
    
    std::vector<std::string> vecsWords;
    std::stringstream ss(theString);
    std::string sIndivStr;
    while(getline(ss, sIndivStr, separator)){
        vecsWords.push_back(sIndivStr);
    }
    return vecsWords;
}

void SolveForX(std::string equation){
    std::vector<std::string> vecEquation = 
            StringToVector(equation, ' ');
    
    // Convert strings to int
    int num1 = std::stoi(vecEquation[2]);
    int num2 = std::stoi(vecEquation[4]);
    int xVal = num2 - num1;
    
    std::cout << "x = " << xVal << "\n";

}
// ----- 1. END PROBLEM : SOLVE FOR X -----

// ----- 2. PROBLEM : RETURN A LIST OF PRIMES -----

std::vector<int> Range(int start, 
        int max, int step);

bool IsPrime(int num);

std::vector<int> GetPrimes(int maxNum);

int main() {
    int num = 0;
    std::cout << "Number to Check : ";
    std::cin >> num;
    
    // Shows bool values as true or false
    std::cout.setf(std::ios::boolalpha);
    std::cout << "Is " << num << " Prime " <<
            IsPrime(num) << "\n";
    
    std::cout << "Generate Primes up to ";
    int maxPrime;
    std::cin >> maxPrime;
    
    std::vector<int> primeList = GetPrimes(maxPrime);
    for(auto x: primeList)
        std::cout << x << "\n";
    
    return 0;
    
}

std::vector<int> Range(int start, int max, 
        int step){
    
    int i = start;
    std::vector<int> range;
    while(i <= max){
        range.push_back(i);
        i += step;
    }
    return range;
}

bool IsPrime(int num){
    for(auto n: Range(2, num - 1, 1)){
        if((num % n) == 0)
            return false;
    }
    return true;
}

std::vector<int> GetPrimes(int maxNum){
    
    std::vector<int> vecPrimes;
    
    for(auto x: Range(2, maxNum, 1)){
        if(IsPrime(x))
            vecPrimes.push_back(x);
    }
    
    return vecPrimes;
}

// ----- 2. END PROBLEM : RETURN A LIST OF PRIMES -----

// ----- 3. PROBLEM : GENERATE A RANDOM VECTOR OF NUMBERS -----

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <numeric>
#include <sstream>

// Needed for random number generation
#include <ctime>

std::vector<int> GenerateRandVec(int numOfNums,
        int min, int max);

int main()
{
    std::vector<int> vecVals = GenerateRandVec(10, 5, 50);
    for(auto x: vecVals)
        std::cout << x << "\n";

    return 0;
}

std::vector<int> GenerateRandVec(int numOfNums,
        int min, int max){
    std::vector<int> vecValues;
    
    // Seed the random number generator
    srand(time(NULL));
    
    int i = 0, randVal = 0;
    
    while(i < numOfNums){
        // The min added on increases result based on min
        // The remainder of modulus can't be greater
        // then the divisor. We have to adjust down
        // based on the addition from min
        randVal = min + std::rand() % ((max + 1) - min);
        vecValues.push_back(randVal);
        i++;
    }
    return vecValues;
}