vigenere.cpp

/*******************************************
 * Name: Vigenére.cpp
 * Author: kongtaoxing
 * Powered by Beijingjiaotong University
 ******************************************/
#include<iostream>
#include<string>
#include<map>
using namespace std;

string encrypt(string s, string key) {
	for(int i = 0; i < s.length(); i++) {
		s[i] = (s[i] - 65 + key[i % key.length()] - 65) % 26 + 65;
	}
	return s;
}

string decrypt(string s, string key) {
	for(int i = 0; i < s.length(); i++) {
		s[i] = (s[i] - key[i % key.length()]) % 26;
		if(s[i] < 0) s[i] += 26;
		s[i] += 65;
	}
	return s;
}

int main() {
	cout << "你想加密还是解密，加密输入e，解密输入d：";
	char c;
	cin >> c;
	cout << "\n请输入需要加/解密的字母串：";
	string s;
	cin >> s;
	for (int i = 0; i < s.length(); i++) {
		if (s[i] >= 97 && s[i] <= 122) {
			s[i] -= 32;
		}
	}
	cout << "\n请输入Key：";
	string key;
	cin >> key;
	for (int i = 0; i < key.length(); i++) {
		if (key[i] >= 97 && key[i] <= 122) {
			key[i] -= 32;
		}
	}
	if (c == 'e') cout << "\n加密后的字符串为：" << encrypt(s, key) << endl;
	else if (c == 'd') cout << "\n解密后的字符串为：" << decrypt(s, key) << endl;
	else cout << "你的输入有误，请重新输入！";
	system("pause");
	return 0;
}