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トップJavaに関する質問複数のインデックスの配列の値の平均をとり、新たな配列に格納したい

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5

追記

2019/01/18 10:44

投稿

LouiS0616
LouiS0616

スコア35660

test CHANGED
@@ -68,13 +68,15 @@
68
68
 
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+ おまけ
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+
71
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  ---
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- 遊び。[Wandbox](https://wandbox.org/permlink/Z1eURC9Rzduaykpf)
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+ 遊び。[Wandbox](https://wandbox.org/permlink/sUXxKujzSuKDdmYS)
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75
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  ```Java
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- List<Double> data = IntStream.iterate(0, pre -> pre+chunkSize)
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+ var data = IntStream.iterate(0, pre -> pre+chunkSize)
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79
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  .takeWhile(val -> val < src.size())
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@@ -99,3 +101,47 @@
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  ;
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  ```
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+
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+
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+
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+ ---
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+
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+ 遊び2。[Wandbox](https://wandbox.org/permlink/rHzztOxTuGLvFx9B)
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+
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+ - リストsumsを追加
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+
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+ - collectしたリストの可変性を保証
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+
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+
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+
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+ ```Java
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+
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+ var sums = IntStream.iterate(0, pre -> pre + chunkSize)
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+
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+ .takeWhile(n -> n < src.size())
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+
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+ .mapToDouble(
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+
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+ val -> src.subList(val, val + chunkSize).stream()
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+
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+ .mapToDouble(n -> n)
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+
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+ .sum()
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+
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+ )
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+
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+ .boxed()
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+
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+ .collect(Collectors.toCollection(ArrayList::new))
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+
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+ ;
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+
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+ var data = sums.stream()
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+
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+ .map(val -> val / chunkSize)
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+
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+ .collect(Collectors.toCollection(ArrayList::new))
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+
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+ ;
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+
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+ ```

4

修正

2019/01/18 10:43

投稿

LouiS0616
LouiS0616

スコア35660

test CHANGED
@@ -70,11 +70,13 @@
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71
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  ---
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- 遊び。
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+ 遊び。[Wandbox](https://wandbox.org/permlink/Z1eURC9Rzduaykpf)
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  ```Java
76
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77
- List<Double> data = IntStream.iterate(0, val -> val < src.size(), pre -> pre+chunkSize)
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+ List<Double> data = IntStream.iterate(0, pre -> pre+chunkSize)
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+
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+ .takeWhile(val -> val < src.size())
78
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79
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  .mapToDouble(
80
82
 
@@ -84,7 +86,7 @@
84
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85
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  .average()
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- .orElse(0.)
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+ .getAsDouble()
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  )
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3

追記

2019/01/18 10:20

投稿

LouiS0616
LouiS0616

スコア35660

test CHANGED
@@ -65,3 +65,35 @@
65
65
  3.5
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66
 
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  ```
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+
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+
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+
71
+ ---
72
+
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+ 遊び。
74
+
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+ ```Java
76
+
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+ List<Double> data = IntStream.iterate(0, val -> val < src.size(), pre -> pre+chunkSize)
78
+
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+ .mapToDouble(
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+
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+ val -> src.subList(val, val+chunkSize).stream()
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+
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+ .mapToDouble(n -> n)
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+
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+ .average()
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+
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+ .orElse(0.)
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+
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+ )
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+
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+ //.peek(System.out::println)
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+
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+ .boxed()
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+
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+ .collect(Collectors.toList())
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+
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+ ;
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+
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+ ```

2

修正

2019/01/18 10:13

投稿

LouiS0616
LouiS0616

スコア35660

test CHANGED
@@ -2,32 +2,66 @@
2
2
 
3
3
  ```Java
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4
 
5
- // 名前が分かりづらいので、data2の名前はsrcに変更
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+ import java.util.*;
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- final int chunkSize = 2;
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+
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+ class Main {
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+
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+ public static void main(String[] args) {
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+
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+ List<Double> src = List.of(1.0, 2.0, 3.0, 4.0);
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+
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+
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+
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+ final int chunkSize = 2;
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+
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- assert src.size() % chunkSize == 0: "分割幅が不適切";
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+ assert src.size() % chunkSize == 0: "分割幅が不適切";
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15
- List<Double> data = new ArrayList<>();
25
+ List<Double> data = new ArrayList<>();
16
26
 
17
- for (int k = 0; k < src.size(); k += chunkSize) {
27
+ for (int i = 0; i < src.size(); i += chunkSize) {
18
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19
- double sum = 0;
29
+ double sum = 0;
20
30
 
21
31
 
22
32
 
23
- for (int i = 0; i < chunkSize; i++) {
33
+ for (int j = 0; j < chunkSize; ++j) {
24
34
 
25
- sum += src.get(i+k);
35
+ sum += src.get(i+j);
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36
 
27
- }
37
+ }
28
38
 
29
- data.add(sum / chunkSize);
39
+ data.add(sum / chunkSize);
40
+
41
+ }
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+
43
+
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+
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+ for(double e: data) {
46
+
47
+ System.out.println(e);
48
+
49
+ }
50
+
51
+ }
30
52
 
31
53
  }
32
54
 
33
55
  ```
56
+
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+
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+
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+ **実行結果** [Wandbox](https://wandbox.org/permlink/XOEcc7ZrDpvO4Fud)
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+
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+ ```
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+
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+ 1.5
64
+
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+ 3.5
66
+
67
+ ```

1

追記

2019/01/18 09:54

投稿

LouiS0616
LouiS0616

スコア35660

test CHANGED
@@ -6,11 +6,13 @@
6
6
 
7
7
 
8
8
 
9
- List<Double> data = new ArrayList<>();
10
-
11
9
  final int chunkSize = 2;
12
10
 
11
+ assert src.size() % chunkSize == 0: "分割幅が不適切";
13
12
 
13
+
14
+
15
+ List<Double> data = new ArrayList<>();
14
16
 
15
17
  for (int k = 0; k < src.size(); k += chunkSize) {
16
18