替代密码包括多种类型，如单表替代密码，多 字母替代密码等。试编程实现一种典型的单表替代密码—凯撒（Caesar）密码。它的加密方法是将明文中的每个字母用此字符在字母表中后面的第k个字母替代。它的加密过程可以表示为下面的函数：E(k)=(m+k)modn ，其中，m为明文字母在字母表中的位置数，n为字母表中的字母个数，k为密钥，E(k)为密文字母在字母表中对应的位置数。-Alternative to passwords, including many types, such as single-table alternative password, multi-letter alternative password. Try programming a typical single-table alternative password- Caesar (Caesar) password. Its encryption method is to express each of the letters in the alphabet with this character in the back of the first k-letter substitution. Its encryption process can be expressed as the following function: E (k) = (m+ K) modn, which, m the letters in the alphabet to express the position number, n is the number of letters in the alphabet, k for Micronesia key, E (k) for the dense text of the mother in the alphabet corresponds to the location of a few.