Question

（语言：scala）

我有一个问题，我想迭代超过100万个数字，但由于某种原因，我得到一个arrayindexOutofbounds异常。我正在使用的功能完美适用于10万个数字，但如果我添加零，我会得到异常。

数组大小不会有问题，因为我构建了一种flex-array，其中数组大约有1000个元素，每个元素都包含一个元素列表。

所以问题看起来像这样：

for (x <- 1 to 1000000) {
  // Do a thing
  }

for for循环只能处理一定数量的元素吗？

我尝试使用“extra-space-flag”运行程序

我将以下整个代码包含在内以供参考，以防它有所作为

object Problem14 {

  class FlexArray (n : Int){
    var array = new Array[List[Tuple2[Int, Int]]](n)
    val size = n

    for(x <- 0 until size) {
      array(x) = List()
    }

    def insert (n : Int, value : Int) {
      if (find(n) != -1) {
     val i = n % size
     array(i) = (n, value) :: array(i)
      }
    }

    def read (i : Int) : List[Tuple2[Int, Int]] = {
      (array(i))
    }

    def findAux (list : List[Tuple2[Int, Int]], n : Int) : Int = {
      if (list == Nil) {
    -1
      } else {
    val (num, value) = list.head
    if (n == num) {
      value
    } else {
      findAux(list.tail, n)
    }
      }
    }

    def find (n : Int) : Int = {
      val i = n % size
      findAux(array(i), n)
    }
  }

  var accArray = new FlexArray(10000)


// denna funktion bör kallas med 1 som andra argument
  def chainLength (n : Int, acc : Int) : Int = {
    if (n == 1) 
      acc
    else {
      val value = accArray.find(n)
    if (value != -1) 
  acc + value 
    else if (n % 2 == 0)
  chainLength(n/2, acc+1)
    else
  chainLength(3*n+1, acc+1)      
    }
  }



 def main(args: Array[String]) {
    var max = 0
    var maxnum = 0

    for (x <- 1 to 1000000) {
      var value = chainLength(x, 1)
      accArray.insert(x, value)
      if (max < value) { 
    max = value
    maxnum = x
      }      

    println(maxnum + ": " + max)

}

}

Answer 1

问题不在于数组索引，scala函数就像java一样，并且将转到Int.MaxValue 2,147,483,647。问题在于chainLength函数中的这一行：

chainLength(3 * n + 1, acc + 1)

由于chainLength在n/2和n * 3 + 1之间自行切换，因此您会遇到大于113383的数字。它会导致整数溢出，因此最终会将一个负值传递给数组索引，从而引发错误。我猜你需要为你的函数添加一些整数溢出处理。

chainLength中对chainLength(113383, 1)的完整输出（以底部溢出结束）：

Starting at 113383
3 * 113383 + 1 = 340150
340150 / 2 = 170075
3 * 170075 + 1 = 510226
510226 / 2 = 255113
3 * 255113 + 1 = 765340
765340 / 2 = 382670
382670 / 2 = 191335
3 * 191335 + 1 = 574006
574006 / 2 = 287003
3 * 287003 + 1 = 861010
861010 / 2 = 430505
3 * 430505 + 1 = 1291516
1291516 / 2 = 645758
645758 / 2 = 322879
3 * 322879 + 1 = 968638
968638 / 2 = 484319
3 * 484319 + 1 = 1452958
1452958 / 2 = 726479
3 * 726479 + 1 = 2179438
2179438 / 2 = 1089719
3 * 1089719 + 1 = 3269158
3269158 / 2 = 1634579
3 * 1634579 + 1 = 4903738
4903738 / 2 = 2451869
3 * 2451869 + 1 = 7355608
7355608 / 2 = 3677804
3677804 / 2 = 1838902
1838902 / 2 = 919451
3 * 919451 + 1 = 2758354
2758354 / 2 = 1379177
3 * 1379177 + 1 = 4137532
4137532 / 2 = 2068766
2068766 / 2 = 1034383
3 * 1034383 + 1 = 3103150
3103150 / 2 = 1551575
3 * 1551575 + 1 = 4654726
4654726 / 2 = 2327363
3 * 2327363 + 1 = 6982090
6982090 / 2 = 3491045
3 * 3491045 + 1 = 10473136
10473136 / 2 = 5236568
5236568 / 2 = 2618284
2618284 / 2 = 1309142
1309142 / 2 = 654571
3 * 654571 + 1 = 1963714
1963714 / 2 = 981857
3 * 981857 + 1 = 2945572
2945572 / 2 = 1472786
1472786 / 2 = 736393
3 * 736393 + 1 = 2209180
2209180 / 2 = 1104590
1104590 / 2 = 552295
3 * 552295 + 1 = 1656886
1656886 / 2 = 828443
3 * 828443 + 1 = 2485330
2485330 / 2 = 1242665
3 * 1242665 + 1 = 3727996
3727996 / 2 = 1863998
1863998 / 2 = 931999
3 * 931999 + 1 = 2795998
2795998 / 2 = 1397999
3 * 1397999 + 1 = 4193998
4193998 / 2 = 2096999
3 * 2096999 + 1 = 6290998
6290998 / 2 = 3145499
3 * 3145499 + 1 = 9436498
9436498 / 2 = 4718249
3 * 4718249 + 1 = 14154748
14154748 / 2 = 7077374
7077374 / 2 = 3538687
3 * 3538687 + 1 = 10616062
10616062 / 2 = 5308031
3 * 5308031 + 1 = 15924094
15924094 / 2 = 7962047
3 * 7962047 + 1 = 23886142
23886142 / 2 = 11943071
3 * 11943071 + 1 = 35829214
35829214 / 2 = 17914607
3 * 17914607 + 1 = 53743822
53743822 / 2 = 26871911
3 * 26871911 + 1 = 80615734
80615734 / 2 = 40307867
3 * 40307867 + 1 = 120923602
120923602 / 2 = 60461801
3 * 60461801 + 1 = 181385404
181385404 / 2 = 90692702
90692702 / 2 = 45346351
3 * 45346351 + 1 = 136039054
136039054 / 2 = 68019527
3 * 68019527 + 1 = 204058582
204058582 / 2 = 102029291
3 * 102029291 + 1 = 306087874
306087874 / 2 = 153043937
3 * 153043937 + 1 = 459131812
459131812 / 2 = 229565906
229565906 / 2 = 114782953
3 * 114782953 + 1 = 344348860
344348860 / 2 = 172174430
172174430 / 2 = 86087215
3 * 86087215 + 1 = 258261646
258261646 / 2 = 129130823
3 * 129130823 + 1 = 387392470
387392470 / 2 = 193696235
3 * 193696235 + 1 = 581088706
581088706 / 2 = 290544353
3 * 290544353 + 1 = 871633060
871633060 / 2 = 435816530
435816530 / 2 = 217908265
3 * 217908265 + 1 = 653724796
653724796 / 2 = 326862398
326862398 / 2 = 163431199
3 * 163431199 + 1 = 490293598
490293598 / 2 = 245146799
3 * 245146799 + 1 = 735440398
735440398 / 2 = 367720199
3 * 367720199 + 1 = 1103160598
1103160598 / 2 = 551580299
3 * 551580299 + 1 = 1654740898
1654740898 / 2 = 827370449
3 * 827370449 + 1 = -1812855948

大数组索引scala

1 个答案: