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Mohawk
Asked:2022-08-17 17:25:24 +0000 UTC2022-08-17 17:25:24 +0000 UTC

如何使用迭代器将列删除或添加到多维列表

  • 772
fun differentGame(row: Int, column: Int, player: String) {
val list: MutableList<MutableList<String>> = mutableListOf(
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","",""),
        mutableListOf("","","","","")
    )

    val iterator = list.iterator()
    while (iterator.hasNext()){
        val item = iterator.next()
        if (list.size > row){
            iterator.remove()
        } else break
    }
}

有这样的代码。在迭代器的帮助下，行被正常删除，但是如何删除或添加列？我试图通过标准 for 循环删除行和列，但它会在那里引发 ConcurrentModificationException。谷歌搜索并通过迭代器找到了异常的解决方案

kotlin list

2 个回答

  1. 这是最简单的示例，将找到的第一个非空元素移动到字符串的末尾。

    val list: MutableList<MutableList<String>> = mutableListOf(
        mutableListOf("","","","",""),
        mutableListOf("","+","","",""),
        mutableListOf("","","!","",""),
        mutableListOf("","","","@",""),
        mutableListOf("","","","","#"),
        mutableListOf("$","","","",""),
        mutableListOf("%","","","",""),
        mutableListOf("*","","","",""),
        mutableListOf("&","","","","")
    )

    println(list)

    val iterator = list.iterator()
    while (iterator.hasNext()) {
        val item = iterator.next()
        val el = item.firstOrNull { it.isNotEmpty() }
        el?.also {
            item.remove(it)
            item.add(it)
        }
    }

    println(list)

    结论

    [[, , , , ], [, +, , , ], [, , !, , ], [, , , @, ], [, , , , #], [$, , , , ], [%, , , , ], [*, , , , ], [&, , , , ]]
[[, , , , ], [, , , , +], [, , , , !], [, , , , @], [, , , , #], [, , , , $], [, , , , %], [, , , , *], [, , , , &]]
    • 0
  2. Best Answer

    在 Kotlin 中，您可以使用工厂方法List()来创建新列表。第一个参数必须是所需的列表元素数量，第二个参数是用于计算列表元素的 lambda。

    例如，您可以像这样得到一个零列表：

    List(5) { 0 } // => [0, 0, 0, 0, 0]

    lambda 有一个参数 - 元素的索引，如果使用它，您可以获得例如非负数的平方列表：

    List(5) { i -> i * i } // => [0, 1, 4, 9, 16]

    lambda 可以有任何返回类型，因此您可以轻松地从空字符串列表创建一个列表：

    List(5) { List(5) { "" } } // => «матрица» 5x5 с пустыми строками

    最后是乘法表：

    List(5) { x -> List(5) { y -> (x + 1) * (y + 1) } }
// [
//   [1,  2,  3,  4,  5],
//   [2,  4,  6,  8, 10],
//   [3,  6,  9, 12, 15],
//   [4,  8, 12, 16, 20],
//   [5, 10, 15, 20, 25]
// ]

    查看官方网站了解其他创建收藏的方式。

    • 0

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