alphabet.cpp

/*
Q1.設計一個程式讓使用者可輸入一個字元，並且判斷使用者
輸入的字元是否為英文字母大小寫，如果是大寫就轉成小寫
輸出，小寫則轉成大寫輸出，不是英文字母則提醒使用者輸
入錯誤。至少可以輸入3次。

*/

// Example program
#include <iostream>
#include <string>

using namespace std;

int main()
{
    char ch;
    for (int i = 0; i < 3; i++) {
        cin >> ch;
        if (ch >= 'a' && ch <= 'z') {
            int diff = 'a' - 'A';
            cout << (char)(ch - diff) << endl;
        } else if (ch >= 'A' && ch <= 'Z') {
            int diff = 'a' - 'A';
            cout << (char)(ch + diff) << endl;
        }else {
            cout << "Invalid input, please input alphabet.\n";
            i--;
        }
    }
    
    cout << "Program is terminated.\n";
    
//   std::string name;
//   std::cout << "What is your name? ";
//   getline (std::cin, name);
//   std::cout << "Hello, " << name << "!\n";
}