#include <iostream>
using namespace std;
#define MINCHAR 32
#define CHARSUM 94
char table[CHARSUM][CHARSUM];
bool Init();
bool Encode(char* key, char* source, char* dest);
bool Dncode(char* key, char* source, char* dest);
int main()
{
	if(!Init())
	{
		cout << "初始化錯誤！" << endl;
		return 1;
	}
	
	char key[256];
	char str1[256];
	char str2[256];
	int operation;
	while(1)
	{
		do
		{
			cout << "請選擇一個操作：1. 加密； 2. 解密； -1. 退出\n";
			cin >> operation;
		}while(operation != -1 && operation != 1 && operation != 2);
		if(operation == -1)
			return 0;
		else if(operation == 1)//加密
		{
			cout << "請輸入密鑰：";
			cin >> key;
			cout << "請輸入待加密字符串：";
			cin >> str1;
			Encode(key, str1, str2);
			cout << "加密后的字符串：" << str2 << endl;
		}
		else if(operation == 2)//解密
		{
			cout << "請輸入密鑰：";
			cin >> key;
			cout << "請輸入待解密字符串：";
			cin >> str1;
			Dncode(key, str1, str2);
			cout << "解密后的字符串：" << str2 << endl;
		}
		cout << endl;
	}
	return 0;
}
// 初始化維吉尼亞方陣
bool Init()
{
	int i, j;
	for(i = 0; i < CHARSUM; i++)
	{
		for(j = 0; j < CHARSUM; j++)
		{
			table[i][j] =MINCHAR + (i + j) % CHARSUM;
		}
	}
	return true;
}
// 加密
// key：密鑰
// source：待加密的字符串
// dest：經過加密后的字符串
bool Encode(char* key, char* source, char* dest)
{
	char* tempSource = source;
	char* tempKey = key;
	char* tempDest = dest;
    do
	{
		*tempDest = table[(*tempKey) - MINCHAR][(*tempSource) - MINCHAR];
		tempDest++;
		if(!(*(++tempKey)))
			tempKey = key;
	}while(*tempSource++);
    dest[strlen(source)] = 0;
	return true;
}
// 解密
// key：密鑰
// source：待解密的字符串
// dest：經過解密后的字符串
bool Dncode(char* key, char* source, char* dest)
{
	char* tempSource = source;
	char* tempKey = key;
	char* tempDest = dest;
	char offset;
    do
	{
		offset = (*tempSource) - (*tempKey);
		offset = offset >= 0 ? offset : offset + CHARSUM;
		*tempDest = MINCHAR + offset;
		tempDest++;
		if(!(*(++tempKey)))
			tempKey = key;
	}while(*++tempSource);
	dest[strlen(source)] = 0;
	return true;
}