回答編集履歴
3
追記
test
CHANGED
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@@ -80,7 +80,7 @@
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80
80
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81
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{
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82
82
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83
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-
std::vector<int> vec;
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83
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std::vector<int> vec; // 単に vec(10) でも良い
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84
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vec.resize(10);
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86
86
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2
修正
test
CHANGED
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@@ -64,9 +64,11 @@
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64
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65
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66
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67
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-
生配列に対しても、sizeofは避
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67
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+
生配列に対しても、sizeofの利用は回避可能です。[std::size](https://cpprefjp.github.io/reference/iterator/size.html)
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68
68
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69
69
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```C++
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70
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+
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71
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#include <iterator>
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72
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#include <vector>
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74
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@@ -108,7 +110,7 @@
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110
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111
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112
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111
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-
**実行結果** [Wandbox](https://wandbox.org/permlink/
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113
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+
**実行結果** [Wandbox](https://wandbox.org/permlink/IwCcylpJ43O4zWpZ)
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112
114
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113
115
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```
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114
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1
追記
test
CHANGED
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@@ -1,4 +1,126 @@
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1
1
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配列というか、std::vectorですね。
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2
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3
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4
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5
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> 下記コードで期待の要素数より少なくなってしまう原因
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6
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7
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8
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9
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生配列と違って、std::vectorはデータを直接保持しないからです。
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10
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11
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```C++
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12
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13
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#include <vector>
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14
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15
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#include <iostream>
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16
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17
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18
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19
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int main()
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20
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21
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{
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22
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std::vector<int> a, b, c;
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24
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25
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26
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27
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a.resize(10);
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28
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29
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b.resize(100);
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30
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31
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c.resize(1000);
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32
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33
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34
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35
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std::cout << sizeof(a) << "\n"
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36
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37
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<< sizeof(b) << "\n"
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38
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39
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<< sizeof(c) << "\n"
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40
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41
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;
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42
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43
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44
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45
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return 0;
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46
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47
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}
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48
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49
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```
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50
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51
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52
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53
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+
**実行結果** [Wandbox](https://wandbox.org/permlink/sEg2rPAH5SPgcOdM)
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54
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55
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```
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56
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57
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24
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58
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59
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24
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60
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61
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24
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62
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63
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```
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64
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65
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66
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67
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+
生配列に対しても、sizeofは避けた方が良いと思います。
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68
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69
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+
```C++
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70
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71
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#include <vector>
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72
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73
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#include <iostream>
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74
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75
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76
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77
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int main()
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78
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79
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{
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80
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81
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std::vector<int> vec;
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82
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+
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83
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vec.resize(10);
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84
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85
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86
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87
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int arr[10];
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88
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89
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90
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91
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std::cout << vec.size() << "\n"
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92
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93
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<< std::size(vec) << "\n"
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94
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95
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<< sizeof(arr) / sizeof(arr[0]) << "\n"
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96
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97
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<< std::size(arr) << "\n"
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98
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99
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;
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100
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+
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101
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102
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103
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return 0;
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104
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105
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+
}
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106
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+
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107
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+
```
|
|
108
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+
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109
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+
|
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110
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+
|
|
111
|
+
**実行結果** [Wandbox](https://wandbox.org/permlink/bZ4nYmqC9AWEYvH7)
|
|
112
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+
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|
113
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+
```
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|
114
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+
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115
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+
10
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116
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+
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117
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+
10
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118
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+
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119
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+
10
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|
120
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+
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121
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+
10
|
|
122
|
+
|
|
123
|
+
```
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|
2
124
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3
125
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4
126
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