回答編集履歴
3
ソースコードの不備(import)を修正
answer
CHANGED
|
@@ -1,10 +1,15 @@
|
|
|
1
1
|
とりあえず。
|
|
2
2
|
|
|
3
3
|
```Java
|
|
4
|
+
import java.util.ArrayList;
|
|
5
|
+
import java.util.Arrays;
|
|
6
|
+
import java.util.Comparator;
|
|
4
|
-
import java.util.
|
|
7
|
+
import java.util.List;
|
|
5
8
|
import java.util.function.BiFunction;
|
|
6
9
|
import java.util.function.Consumer;
|
|
10
|
+
import java.util.function.Function;
|
|
7
11
|
import java.util.stream.Collectors;
|
|
12
|
+
import java.util.stream.IntStream;
|
|
8
13
|
|
|
9
14
|
public class Sorters {
|
|
10
15
|
|
|
@@ -23,6 +28,12 @@
|
|
|
23
28
|
.findFirst()
|
|
24
29
|
.orElse(0);
|
|
25
30
|
|
|
31
|
+
static Function<Integer,Comparator<long[]>> genComparatorChain = size ->
|
|
32
|
+
IntStream.range(0,size)
|
|
33
|
+
.mapToObj(i -> Comparator.<long[],Long>comparing(x -> x[i]))
|
|
34
|
+
.reduce((a,b) -> 0, Comparator::thenComparing);
|
|
35
|
+
static Comparator<long[]> comparator14 = genComparatorChain.apply(2);
|
|
36
|
+
|
|
26
37
|
static BiFunction<Comparator<long[]>, long[][], long[][]> sorter =
|
|
27
38
|
(comparator, array) -> Arrays.stream(array)
|
|
28
39
|
.sorted(comparator)
|
|
@@ -43,7 +54,8 @@
|
|
|
43
54
|
dump_.accept(sorter.apply(comparator3,a));
|
|
44
55
|
dump_.accept(sorter.apply(comparator4,a));
|
|
45
56
|
dump_.accept(sorter.apply(comparator13,a));
|
|
46
|
-
dump_.accept(sorter.apply(comparator12,a));
|
|
57
|
+
dump_.accept(sorter.apply(comparator12,a));
|
|
58
|
+
dump_.accept(sorter.apply(comparator14,a));
|
|
47
59
|
}
|
|
48
60
|
}
|
|
49
61
|
```
|
2
配列のサイズに合わせたComparator<long[]>(追記)
answer
CHANGED
|
@@ -64,4 +64,17 @@
|
|
|
64
64
|
// 3
|
|
65
65
|
Function<Integer,Function<long[],Long>> getElement = i -> (array) -> array[i];
|
|
66
66
|
Comparator<long[]> comparator13 = Comparator.comparing(getElement.apply(0)).thenComparing(getElement.apply(1));
|
|
67
|
-
```
|
|
67
|
+
```
|
|
68
|
+
###
|
|
69
|
+
**配列のサイズに合わせたComparator<long[]>(追記)**
|
|
70
|
+
|
|
71
|
+
結論の３番目を変形して、配列のサイズに応じた`Comparator<long[]>`が作れることがわかりました。
|
|
72
|
+
|
|
73
|
+
```Java
|
|
74
|
+
Function<Integer,Comparator<long[]>> genComparatorChain = size ->
|
|
75
|
+
IntStream.range(0,size)
|
|
76
|
+
.mapToObj(i -> Comparator.<long[],Long>comparing(x -> x[i]))
|
|
77
|
+
.reduce((a,b) -> 0, Comparator::thenComparing);
|
|
78
|
+
Comparator<long[]> comparator14 = genComparatorChain.apply(2);
|
|
79
|
+
```
|
|
80
|
+
結論：Comparatorに限らず、Functionインターフェイスでもreduce()を使って、compose()、andThen()をチェインできることがわかり有益でした。
|
1
結論(追記)
answer
CHANGED
|
@@ -13,6 +13,16 @@
|
|
|
13
13
|
static Comparator<long[]> comparator3 = Comparator.<long[], Long>comparing(v -> v[0]).thenComparing(v -> v[1]);
|
|
14
14
|
static Comparator<long[]> comparator4 = Comparator.<long[], Long>comparing(v -> v[0]).thenComparingLong(v -> v[1]);
|
|
15
15
|
|
|
16
|
+
static Function<Integer,Function<long[],Long>> getElement = i -> (array) -> array[i];
|
|
17
|
+
static Comparator<long[]> comparator13 = Comparator.comparing(getElement.apply(0)).thenComparing(getElement.apply(1));
|
|
18
|
+
|
|
19
|
+
static Comparator<long[]> comparator12 = (x,y) ->
|
|
20
|
+
IntStream.range(0, Math.min(x.length,y.length))
|
|
21
|
+
.map(i -> Long.compare(x[i], y[i]))
|
|
22
|
+
.dropWhile(i -> i == 0)
|
|
23
|
+
.findFirst()
|
|
24
|
+
.orElse(0);
|
|
25
|
+
|
|
16
26
|
static BiFunction<Comparator<long[]>, long[][], long[][]> sorter =
|
|
17
27
|
(comparator, array) -> Arrays.stream(array)
|
|
18
28
|
.sorted(comparator)
|
|
@@ -31,7 +41,27 @@
|
|
|
31
41
|
dump_.accept(sorter.apply(comparator1,a));
|
|
32
42
|
dump_.accept(sorter.apply(comparator2,a));
|
|
33
43
|
dump_.accept(sorter.apply(comparator3,a));
|
|
34
|
-
dump_.accept(sorter.apply(comparator4,a));
|
|
44
|
+
dump_.accept(sorter.apply(comparator4,a));
|
|
45
|
+
dump_.accept(sorter.apply(comparator13,a));
|
|
46
|
+
dump_.accept(sorter.apply(comparator12,a));
|
|
35
47
|
}
|
|
36
48
|
}
|
|
49
|
+
```
|
|
50
|
+
###
|
|
51
|
+
**結論(追記)**
|
|
52
|
+
|
|
53
|
+
`thenComparing`のkyExtractorの型が推論されない問題の解決として、以下の３つの方法がありました。
|
|
54
|
+
|
|
55
|
+
- Comparator.comparingに指定するラムダ式の、引数に型`long[]`を指定する
|
|
56
|
+
- staticメソッドComparator.comparingにkeyExtractorの型`<long[], Long>`を指定する
|
|
57
|
+
- あらかじめkeyExtractor関数`Function<long[],Long>`を定義しておき渡す。
|
|
58
|
+
|
|
59
|
+
```Java
|
|
60
|
+
// 1
|
|
61
|
+
Comparator.comparing((long[] v) -> v[0]).thenComparing(v -> v[1]);
|
|
62
|
+
// 2
|
|
63
|
+
Comparator.<long[], Long>comparing(v -> v[0]).thenComparing(v -> v[1]);
|
|
64
|
+
// 3
|
|
65
|
+
Function<Integer,Function<long[],Long>> getElement = i -> (array) -> array[i];
|
|
66
|
+
Comparator<long[]> comparator13 = Comparator.comparing(getElement.apply(0)).thenComparing(getElement.apply(1));
|
|
37
67
|
```
|