Dart-如何初始化锯齿状数组? [英] Dart - How to initialize a jagged array?
问题描述
我正在尝试初始化一个交错的零数组.我以为 List :: filled
是要走的路,但是我错了.
I'm trying to initialize a jagged array of zeroes. I thought List::filled
is the way to go, but I was wrong.
void main() {
List<List<int>> matrix = new List.filled(4, new List<int>.filled(4, 0));
print('before: $matrix');
matrix[2][3] = 1; // change a single cell
print('after: $matrix');
}
输出不正确.尽管使用了 new
关键字,但Dart还是重用了子列表:
Output is not correct. Despite of the new
keyword, Dart reused sublists:
之前:[[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0]]
之后:[[0,0,0,1],[0,0,0,1],[0,0,0,1],[0,0,0,1]]
before: [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
after: [[0, 0, 0, 1], [0, 0, 0, 1], [0, 0, 0,1], [0, 0, 0, 1]]
初始化锯齿数组的正确方法是什么,以使每个子数组不仅仅是指向同一列表的指针?
What's the correct way to initialize a jagged array, so that each sub array are not merely pointers to the same list?
推荐答案
如果每个索引应具有唯一值,请使用 List.generate
而不是 List.filled
:>
Use List.generate
instead of List.filled
if each index should have unique value:
var matrix = List.generate(4, (_) => List.filled(4, 0));
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