为了把一个原文本串x[1..m]转化成目的串y[1..n],可以执行各种转换操作，目的是，给定的x和y，产生一系列的转换把x变成y,每一个转换操作都有一个相关的代价。我们假设每个操作的代价是已知的常数。此外，还假设复制和替换的单个代价小于删除和插入操作的合并代价；一个给定的转换操作序列的代价等于序列中单个操作的代价之和。-In order to bring a text of the string x [1 .. m] into the purpose string y [1 .. n], can perform a variety of conversion operations, the purpose is, given x and y, produces a series of conversion to x variable into y, each conversion operation has an associated price. We assume that the cost of each operation are known constants. In addition, assume that a single copy and replace the price is less than the combined deletion and insertion costs　a given sequence of conversion price equal to the sequence of individual operations and the costs.