Question

  class Buffer(s: String) {

  import scala.collection.mutable.StringBuilder
  import scala.io.StdIn

  private var buffer: StringBuilder = new StringBuilder(s)
  private var cursor: Int = 0  // cursor is in between characters
  private var marker: Int = 0  // marker is in between characters
  private var paste: String = ""
  private def end: Int = buffer.length              // the end of the line
  private def lwr: Int = Math.min(marker, cursor)
  private def upr: Int = Math.max(marker, cursor)

  /*
   * Accessor methods to return aspects of the state
   */
  def getCursor: Int = cursor
  def getMarker: Int = marker
  def getString: String = buffer.toString
  def getPaste: String = paste


          /**
       * Delete Duplicate characters.  Within the defined region, for each character,
       * if it occurs once then keep it, but if it occurs multiple times then keep
       * only the first occurrence.  The characters to the left and right of the
       * defined region remain unchanged, but within the defined region the duplicates
       * are removed. This operation does not affect the paste buffer. The cursor is
       * placed finally at the lower end of the defined region and the marker is placed
       * finally at the upper end of the (probably reduced) defined region. For example:
       * 
       *     m i s s i s s i p p i       marker =  1       
       *      ^                 ^        cursor = 10
       *
       * Then perform  sc('a', 'X')
       * 
       *     m i s p i      marker = 1       
       *      ^     ^       cursor = 4
       */
      def dd() 
      {
        var droppedchars: Int = 0;
         for (x <- lwr until upr)
         {
           var c = buffer.charAt(x)
           for (i <- lwr until upr)
           {
             if (buffer.charAt(i) == c)
             {
               buffer.deleteCharAt(i)
               droppedchars += 1

             }
           }
           marker = lwr
           cursor = upr - droppedchars


         }
      }

也需要一些这方面的帮助，似乎不起作用函数需要删除它找到的任何重复字符，将标记移回新定义区域的开头，将光标移动到新定义区域的末尾，而不是要求有人为我写这个，只是指导我正确的方向

Answer 1

为什么不呢：

library(tidyverse)
library(shiny)

ui <- fluidPage(
  selectInput("select1", "select quarter", choices  = unique(df$period)),
  verbatimTextOutput(outputId = "val")

)

server <- function(input, output) {


  v1 <- reactive({        

    i1 <- match(input$select1, df$period) # get the index
    i2 <- seq(pmax(1, i1-1), i1, by = 1) # create a sequence from the previous row

    df %>% 
      slice(i2) %>% #slice the rows
      pull(value) %>% # pull the value column
      diff %>% # get the difference of the two values
      .[1] #to make sure that we get NA if we select Q1

  })
  output$val <- renderText({
    v1()
  })

}
shinyApp(ui = ui, server = server)

Answer 2

您尝试做的事情从性能角度看O（n ^ 2）不是很好...... Imo，一个更好的解决方案是在缓冲区上只使用一个循环，并在其中使用一组字符（在for循环外声明）检查每个字符c：

val  chars = scala.collection.mutable.Set[Char]()

...

for (x <- lwr until upr) {
  var c = buffer.charAt(x)
  if (chars contains c) buffer.deleteCharAt(x) else chars += c
}
cursor = marker + chars.size

stringbuilder Scala删除重复的字符

2 个答案: