如何从右边用分隔符分割字符串?
例如
scala> "hello there how are you?".rightSplit(" ", 1)
res0: Array[java.lang.String] = Array(hello there how are, you?)
Python 有一个
.rsplit()
方法,这就是我在 Scala 中所追求的:
In [1]: "hello there how are you?".rsplit(" ", 1)
Out[1]: ['hello there how are', 'you?']
我认为最简单的解决方案是搜索索引位置,然后基于该位置进行拆分。例如:
scala> val msg = "hello there how are you?"
msg: String = hello there how are you?
scala> msg splitAt (msg lastIndexOf ' ')
res1: (String, String) = (hello there how are," you?")
既然有人评论了
lastIndexOf
返回 -1,那么这个解决方案就完全没问题了:
scala> val msg = "AstringWithoutSpaces"
msg: String = AstringWithoutSpaces
scala> msg splitAt (msg lastIndexOf ' ')
res0: (String, String) = ("",AstringWithoutSpaces)
您可以使用普通的旧正则表达式:
scala> val LastSpace = " (?=[^ ]+$)"
LastSpace: String = " (?=[^ ]+$)"
scala> "hello there how are you?".split(LastSpace)
res0: Array[String] = Array(hello there how are, you?)
(?=[^ ]+$)
表示我们将向前 (?=
) 查找一组长度至少为 1 个字符的非空格 ([^ ]
) 字符。最后,这个空格后跟这样的序列必须位于字符串的末尾:$
。
如果只有一个令牌,此解决方案不会中断:
scala> "hello".split(LastSpace)
res1: Array[String] = Array(hello)
scala> val sl = "hello there how are you?".split(" ").reverse.toList
sl: List[String] = List(you?, are, how, there, hello)
scala> val sr = (sl.head :: (sl.tail.reverse.mkString(" ") :: Nil)).reverse
sr: List[String] = List(hello there how are, you?)
迭代使用
lastIndexOf
和 substring
进行分割。
object Main {
def rsplit(string: String, delimiter: String, maxSplits: Int): Array[String] = {
var remainingSplits = maxSplits
var str = string
var result = List[String]()
while (remainingSplits > 0) {
val pos = str.lastIndexOf(delimiter)
if (pos == -1) {
result = str :: result
remainingSplits = 0
str=""
} else {
result = str.substring(pos + delimiter.length) :: result
str = str.substring(0, pos)
remainingSplits -= 1
}
}
if (str.nonEmpty || maxSplits == 0) {
result = str :: result
}
result.toArray
}
def myPrint(stringArray: Array[String]): Unit= {
println("["++stringArray.map("\'"++_++"\'").mkString(", ")++"]");
}
def main(args: Array[String]): Unit = {
// Test cases
myPrint(rsplit("bor tor tor tor", "tor", 2)) // More than maxSplits
myPrint(rsplit("bor tor tor", "tor", 2)) // Exactly equal to maxSplits
myPrint(rsplit("bor tor", "tor", 2)) // Less than maxSplits
}
}