在Scala中重写PHP的similar_text

Question

为了重写PHP的similar_text算法,我尝试了一些不同的方法.所有这些都取得了一定的成功,但最终以失败告

第一次尝试:我尝试从PHP源代码重写它.C优雅地使用指针使得在Scala中看起来无法做出同样精确的实现并且干净利落.

第二次尝试:我尝试用java中的PHP Similar_text()上发布的Java函数重写它.不幸的是,这个函数在Java中不起作用所以永远不要把它移植到Scala上.

第三次(当前)尝试:我目前正在尝试将此JavaScript实现转换为Scala:http://phpjs.org/functions/similar_text/.我以前在JavaScript中使用它,它似乎正常运行.我在Scala中的翻译(下面)运行不正常.它可以让你在1或2个相似性索引中,但它通常不是它的PHP对应结果的100%.

def similartext(first:String,second:String) : Int = {
  if (first == null || second == null) {
    0
  }

  var pos1:Int = 0
  var pos2:Int = 0
  var max:Int = 0
  var sum:Int = 0
  var l:Int = 0

  val firstLength:Int = first.length
  val secondLength:Int = second.length

  for (p <- 0 until firstLength) {
    for (q <- 0 until secondLength) {
      while(p+l < firstLength && q+l < secondLength && (first.charAt(p+l) == second.charAt(q+l))) {
        if (l > max) {
            println("[" + p + "," + q + "," + l + "]" + first.charAt(p+l) + " | " + second.charAt(q+l))
            max = l
            pos1 = p
            pos2 = q
          }
        l += 1
      }
    }
  }

  sum = max;

  if (sum > 0) {
    if (pos1 > 0 && pos2 > 0) {
      sum += similartext(first.substring(0, pos2), second.substring(0, pos2))
    }

    if ((pos1 + max < firstLength) && (pos2 + max < secondLength)) {
      sum += similartext(first.substring(pos1 + max, (pos1 + max) + (firstLength - pos1 - max)), second.substring(pos2 + max, (pos2 + max) + (secondLength - pos2 - max)))
    }
  }

  sum;
}

测试:

(Scala)val st = similartext("apple","aple") Yields 3
(PHP)$similar = similar_text("apple","aple"); Yields 4

(Scala)val st = similartext("starbucks","stharducks") Yields 8
(PHP)$similar = similar_text("starbucks","stharducks"); Yields 8

(Scala)val st = similartext("hello earth!","hello world!") Yields 10
(PHP)$similar = similar_text("hello earth!","hello world!"); Yields 8

有没有人对这里出了什么问题有任何想法？

Answer 1

这是一个提示:仔细查看JavaScript版本的第28行 - 特别是该行的最后一个字符.这就是你的实现不同的地方.(l对于每对索引,您也不会重置为零,但这不是最重要的问题.)

var顺便说一下,这是一个免费的Scala版本:

def similarText(x: String, y: String): Int = {
  val indices = for {
    (s, p) <- x.tails.zipWithIndex
    (t, q) <- y.tails.zipWithIndex
    l = ((s zip t) takeWhile Function.tupled(_ == _)).size
  } yield (p, q, l)
  val (pos1, pos2, max) = indices.maxBy(_._3)

  if (max == 0) max else max +
    similarText(x take pos1, y take pos2) +
    similarText(x drop (pos1 + max), y drop (pos2 + max))
}

这是相当不合适的 - 我相信你可以很容易地使它更加简洁和高效.

而对于加分:有在JavaScript中的错误版本尝试,例如"aabcd"和"abcabcd",其结果将是不一样的,因为PHP的(或地雷).