[NOIP2012 提高组] Vigenère 密码
题目描述
16 世纪法国外交家 Blaise de Vigenère 设计了一种多表密码加密算法 Vigenère 密码。Vigenère 密码的加密解密算法简单易用，且破译难度比较高，曾在美国南北战争中为南军所广泛使用。
在密码学中，我们称需要加密的信息为明文，用 M M M 表示；称加密后的信息为密文，用 C C C 表示；而密钥是一种参数，是将明文转换为密文或将密文转换为明文的算法中输入的数据，记为 k k k。在 Vigenère 密码中，密钥 k k k 是一个字母串， k = k 1 , k 2 , … , k n k=k_1,k_2,…,k_n k=k1,k2,…,kn。当明文 M = m 1 , m 2 , … , m n M=m_1,m_2,…,m_n M=m1,m2,…,mn 时，得到的密文 C = c 1 , c 2 , … , c n C=c_1,c_2,…,c_n C=c1,c2,…,cn，其中 c i c_i ci= m i ® k i m_i \operatorname{\circledR} k_i mi®ki，运算 ® \circledR ® 的规则如下表所示：
® A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A A B C D E F G H I J K L M N O P Q R S T U V W X Y Z B B C D E F G H I J K L M N O P Q R S T U V W X Y Z A C C D E F G H I J K L M N O P Q R S T U V W X Y Z A B D D E F G H I J K L M N O P Q R S T U V W X Y Z A B C E E F G H I J K L M N O P Q R S T U V W X Y Z A B C D F F G H I J K L M N O P Q R S T U V W X Y Z A B C D E G G H I J K L M N O P Q R S T U V W X Y Z A B C D E F H H I J K L M N O P Q R S T U V W X Y Z A B C D E F G I I J K L M N O P Q R S T U V W X Y Z A B C D E F G H J J K L M N O P Q R S T U V W X Y Z A B C D E F G H I K K L M N O P Q R S T U V W X Y Z A B C D E F G H I J L L M N O P Q R S T U V W X Y Z A B C D E F G H I J K M M N O P Q R S T U V W X Y Z A B C D E F G H I J K L N N O P Q R S T U V W X Y Z A B C D E F G H I J K L M O O P Q R S T U V W X Y Z A B C D E F G H I J K L M N P P Q R S T U V W X Y Z A B C D E F G H I J K L M N O Q Q R S T U V W X Y Z A B C D E F G H I J K L M N O P R R S T U V W X Y Z A B C D E F G H I J K L M N O P Q S S T U V W X Y Z A B C D E F G H I J K L M N O P Q R T T U V W X Y Z A B C D E F G H I J K L M N O P Q R S U U V W X Y Z A B C D E F G H I J K L M N O P Q R S T V V W X Y Z A B C D E F G H I J K L M N O P Q R S T U W W X Y Z A B C D E F G H I J K L M N O P Q R S T U V X X Y Z A B C D E F G H I J K L M N O P Q R S T U V W Y Y Z A B C D E F G H I J K L M N O P Q R S T U V W X Z Z A B C D E F G H I J K L M N O P Q R S T U V W X Y \begin{array}{c|cccccccccccccccccccccccccc} \circledR &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} \\\hline \tt A &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} \\ \tt B &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} \\ \tt C &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} \\ \tt D &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} \\ \tt E &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} \\ \tt F &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} \\ \tt G &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} \\ \tt H &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} \\ \tt I &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} \\ \tt J &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} \\ \tt K &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} \\ \tt L &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} \\ \tt M &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} \\ \tt N &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} \\ \tt O &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} \\ \tt P &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} \\ \tt Q &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} \\ \tt R &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} \\ \tt S &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} \\ \tt T &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} \\ \tt U &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} \\ \tt V &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} \\ \tt W &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} \\ \tt X &\tt X \kern{-5pt} &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} \\ \tt Y &\tt Y \kern{-5pt} &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} \\ \tt Z &\tt Z \kern{-5pt} &\tt A \kern{-5pt} &\tt B \kern{-5pt} &\tt C \kern{-5pt} &\tt D \kern{-5pt} &\tt E \kern{-5pt} &\tt F \kern{-5pt} &\tt G \kern{-5pt} &\tt H \kern{-5pt} &\tt I \kern{-5pt} &\tt J \kern{-5pt} &\tt K \kern{-5pt} &\tt L \kern{-5pt} &\tt M \kern{-5pt} &\tt N \kern{-5pt} &\tt O \kern{-5pt} &\tt P \kern{-5pt} &\tt Q \kern{-5pt} &\tt R \kern{-5pt} &\tt S \kern{-5pt} &\tt T \kern{-5pt} &\tt U \kern{-5pt} &\tt V \kern{-5pt} &\tt W \kern{-5pt} &\tt X \kern{-5pt} &\tt Y \kern{-5pt} \\ \end{array} ®ABCDEFGHIJKLMNOPQRSTUVWXYZAABCDEFGHIJKLMNOPQRSTUVWXYZBBCDEFGHIJKLMNOPQRSTUVWXYZACCDEFGHIJKLMNOPQRSTUVWXYZABDDEFGHIJKLMNOPQRSTUVWXYZABCEEFGHIJKLMNOPQRSTUVWXYZABCDFFGHIJKLMNOPQRSTUVWXYZABCDEGGHIJKLMNOPQRSTUVWXYZABCDEFHHIJKLMNOPQRSTUVWXYZABCDEFGIIJKLMNOPQRSTUVWXYZABCDEFGHJJKLMNOPQRSTUVWXYZABCDEFGHIKKLMNOPQRSTUVWXYZABCDEFGHIJLLMNOPQRSTUVWXYZABCDEFGHIJKMMNOPQRSTUVWXYZABCDEFGHIJKLNNOPQRSTUVWXYZABCDEFGHIJKLMOOPQRSTUVWXYZABCDEFGHIJKLMNPPQRSTUVWXYZABCDEFGHIJKLMNOQQRSTUVWXYZABCDEFGHIJKLMNOPRRSTUVWXYZABCDEFGHIJKLMNOPQSSTUVWXYZABCDEFGHIJKLMNOPQRTTUVWXYZABCDEFGHIJKLMNOPQRSUUVWXYZABCDEFGHIJKLMNOPQRSTVVWXYZABCDEFGHIJKLMNOPQRSTUWWXYZABCDEFGHIJKLMNOPQRSTUVXXYZABCDEFGHIJKLMNOPQRSTUVWYYZABCDEFGHIJKLMNOPQRSTUVWXZZABCDEFGHIJKLMNOPQRSTUVWXY
Vigenère 加密在操作时需要注意：
- ® \circledR ® 运算忽略参与运算的字母的大小写，并保持字母在明文 M M M 中的大小写形式；
- 当明文 M M M 的长度大于密钥 k k k 的长度时，将密钥 k k k 重复使用。
例如，明文 M = Helloworld M=\texttt{Helloworld} M=Helloworld，密钥 k = abc k=\texttt{abc} k=abc 时，密文 C = Hfnlpyosnd C=\texttt{Hfnlpyosnd} C=Hfnlpyosnd。
明文 H e l l o w o r l d 密钥 a b c a b c a b c a 密文 H f n l p y o s n d \begin{array}{|c|c|c|c|c|c|c|c|c|c|c|} \hline \textsf{明文} & \tt H & \tt e & \tt l & \tt l & \tt o & \tt w & \tt o & \tt r & \tt l & \tt d \\ \hline \textsf{密钥} & \tt a & \tt b & \tt c & \tt a & \tt b & \tt c & \tt a & \tt b & \tt c & \tt a \\ \hline \textsf{密文} & \tt H & \tt f & \tt n & \tt l & \tt p & \tt y & \tt o & \tt s & \tt n & \tt d \\ \hline \end{array} 明文密钥密文HaHebflcnlalobpwcyoaorbslcndad
输入格式
共 2 行。
第一行为一个字符串，表示密钥 k k k，长度不超过 100 100 100，其中仅包含大小写字母。
第二行为一个字符串，表示经加密后的密文，长度不超过 1000 1000 1000，其中仅包含大小写字母。
输出格式
一个字符串，表示输入密钥和密文所对应的明文。
样例 #1
样例输入 #1
CompleteVictory
Yvqgpxaimmklongnzfwpvxmniytm
样例输出 #1
Wherethereisawillthereisaway
提示
对于 100 % 100\% 100% 的数据，输入的密钥的长度不超过 100 100 100，输入的密文的长度不超过 1000 1000 1000，且都仅包含英文字母。
NOIP 2012 提高组 第一天 第一题
分析
此题并不难理解，关键是如何求出明文，不难看出，当密钥（K）与密文（C）均为大写时且长度为1时，有明文（M）满足
M = ( C − K + 26 ) % 26 + ’ A ’ M=(C-K+26)\%26+ \texttt{'} A \texttt{'} M=(C−K+26)%26+’A’
所以可以一个一个转换
代码
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
#define int long long
const int M=1e5;
int read(int &x){scanf("%lld",&x);return x;
}
void print(int x,const char* mw){printf("%lld",x);printf(mw);
}
char turn(char mw,char my){return (mw-my+26)%26+'A';
}
char k[M],c[M];
bool vis[M];
signed main(){
// freopen("vigenere.in","r",stdin);
// freopen("vigenere.out","w",stdout);scanf("%s",k+1);scanf("%s",c+1);int s_k=strlen(k+1),s_c=strlen(c+1);for(int i=1;i<=s_k;i++) k[i]=toupper(k[i]);for(int i=1;i<=s_c;i++){if('a'<=c[i] and c[i]<='z') vis[i]=1;c[i]=toupper(c[i]);}int j=1;for(int i=1;i<=s_c;i++){char m=turn(c[i],k[j++]);if(vis[i]) m=tolower(m);printf("%c",m);if(j>s_k) j=1;}
// fclose(stdin);fclose(stdout);return 0;
}
