设A 和B 是2 个字符串。要用最少的字符操作将字符串A 转换为字符串B。这里所说的字符操作包括

(1)删除一个字符；

(2)插入一个字符；

(3)将一个字符改为另一个字符。

将字符串A变换为字符串B 所用的最少字符操作数称为字符串A到B 的编辑距离，记为d(A,B)。试设计一个有效算法，对任给的2 个字符串A和B，计算出它们的编辑距离d(A,B)。-For A and B are two strings. Operation to use at least the characters will be converted to string A string B. Operation of the characters mentioned here, including (1) delete a character　(2) insert a character　(3) will be replaced by one character to another character. Will transform the string A string B for at least the characters used in string operands as the editor of A to B distance is recorded as d (A, B). Test the design of an efficient algorithm, for any given two strings A and B, to calculate their edit distance d (A, B).