QSet使用及Qt自定义类型使用QHash等算法

﹏ヽ暗。殇╰゛Y 2021-10-01 06:10 468阅读 0赞

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本文标题：QSet使用及Qt自定义类型使用QHash等算法     本文地址： [http://techieliang.com/2017/12/580/][http_techieliang.com_2017_12_580]

**文章目录**

*  [1. 介绍][1.]
 *  [2. 简单范例][2.]
 *  [3. 自定义类型][3.]

## 1. 介绍 ##

Qt提供的一个单值的数学集合的快速查找容器，使用方式与QList相同，但其内元素不会有重复。详细说明见 [官方文档][Link 1]

> 注意，此容器实现方式是基于哈希表，而不是红黑树，若使用自定义类必须提供对应的hash函数：
> 
> [QSet][Link 1]‘s value data type must be an [assignable data type][]. You cannot, for example, store a [QWidget][] as a value; instead, store a [QWidget][] \*. In addition, the type must provide `operator==()`, and there must also be a global [qHash][]() function that returns a hash value for an argument of the key’s type. See the [QHash][] documentation for a list of types supported by [qHash][]().

## 2. 简单范例 ##

1.  QSet <QString> m\_set;
2.  m\_set.insert("1");
3.  m\_set.insert("3");
4.  m\_set.insert("2");//注意插入顺序
5.  auto b\_set = m\_set.begin();
6.  qDebug()<<m\_set.size();
7.  qDebug()<<\*b\_set++;
8.  qDebug()<<\*b\_set++;
9.  qDebug()<<\*b\_set++;//注意存储顺序
10. m\_set.insert("1");//插入重复的
11. b\_set = m\_set.begin();
12. qDebug()<<m\_set.size();
13. qDebug()<<\*b\_set++;
14. qDebug()<<\*b\_set++;
15. qDebug()<<\*b\_set++;

结果

1.  3
2.  "1"
3.  "2"
4.  "3"
5.  3
6.  "1"
7.  "2"
8.  "3"

## 3. 自定义类型 ##

1.  \#include <QCoreApplication>
2.  \#include <QSet>
3.  \#include <QDebug>
4.  class testCustomTypeByQSet \{ 
5.  public:
6.  testCustomTypeByQSet(int v):m\_value(v)\{ \};
7.  int value() const\{ 
8.  return m\_value;
9.  \}
10. bool operator == (const testCustomTypeByQSet &t) const \{ 
11. return (m\_value==t.value());
12. \}
13. private:
14. int m\_value;
15. \};
16. uint qHash(const testCustomTypeByQSet &key, uint seed = 0) \{ 
17. return key.value();
18. \}
19. int main(int argc, char \*argv\[\]) \{ 
20. QCoreApplication a(argc, argv);
21. QSet<testCustomTypeByQSet> m\_set;
22. m\_set.insert(testCustomTypeByQSet(1));
23. m\_set.insert(testCustomTypeByQSet(3));
24. m\_set.insert(testCustomTypeByQSet(2));
25. m\_set.insert(testCustomTypeByQSet(7));
26. m\_set.insert(testCustomTypeByQSet(-1));
27. auto b\_set = m\_set.begin();
28. qDebug()<<m\_set.size();
29. qDebug()<<(\*b\_set++).value();
30. qDebug()<<(\*b\_set++).value();
31. qDebug()<<(\*b\_set++).value();
32. qDebug()<<(\*b\_set++).value();
33. qDebug()<<(\*b\_set++).value();
34. return 0;
35. \}

结果

1.  5
2.  \-1
3.  1
4.  2
5.  3
6.  7

qt自身的类已经实现了对应的qHash，存储在QHash类中，详见[官方文档][Link 2]：

1.  uint qHash(const QXmlNodeModelIndex &index)
2.  uint qHash(const QUrl &url, uint seed = 0)
3.  uint qHash(const QDateTime &key, uint seed = 0)
4.  uint qHash(const QDate &key, uint seed = 0)
5.  uint qHash(const QTime &key, uint seed = 0)
6.  uint qHash(const QPair<T1, T2> &key, uint seed = 0)
7.  uint qHash(const std::pair<T1, T2> &key, uint seed = 0)
8.  uint qHash(char key, uint seed = 0)
9.  uint qHash(uchar key, uint seed = 0)
10. uint qHash(signed char key, uint seed = 0)
11. uint qHash(ushort key, uint seed = 0)
12. uint qHash(short key, uint seed = 0)
13. uint qHash(uint key, uint seed = 0)
14. uint qHash(int key, uint seed = 0)
15. uint qHash(ulong key, uint seed = 0)
16. uint qHash(long key, uint seed = 0)
17. uint qHash(quint64 key, uint seed = 0)
18. uint qHash(qint64 key, uint seed = 0)
19. uint qHash(float key, uint seed = 0)
20. uint qHash(double key, uint seed = 0)
21. uint qHash(const QChar key, uint seed = 0)
22. uint qHash(const QByteArray &key, uint seed = 0)
23. uint qHash(const QBitArray &key, uint seed = 0)
24. uint qHash(const QString &key, uint seed = 0)
25. uint qHash(const QStringRef &key, uint seed = 0)
26. uint qHash(QLatin1String key, uint seed = 0)
27. uint qHash(const T \*key, uint seed = 0)
28. uint qHash(const QHash<Key, T> &key, uint seed = 0)
29. uint qHash(const QSet<T> &key, uint seed = 0)
30. uint qHash(const QVersionNumber &key, uint seed = 0)
31. uint qHash(const QSslCertificate &key, uint seed = 0)
32. uint qHash(QSslEllipticCurve curve, uint seed = 0)
33. uint qHash(const QSslError &key, uint seed = 0)
34. uint qHash(const QGeoCoordinate &coordinate, uint seed = 0)

同时也在对应类中做了“==”的重载操作符，比如[QString类][QString]。

转载请以链接形式标明本文标题和地址： [Techie亮博客][Techie 1] » [QSet使用及Qt自定义类型使用QHash等算法][http_techieliang.com_2017_12_580]

转载于:https://www.cnblogs.com/techiel/p/7999389.html

[Techie]: http://www.techieliang.com/
[http_techieliang.com_2017_12_580]: http://techieliang.com/2017/12/580/
[1.]: http://techieliang.com/2017/12/580/#title-0
[2.]: http://techieliang.com/2017/12/580/#title-1
[3.]: http://techieliang.com/2017/12/580/#title-2
[Link 1]: http://doc.qt.io/qt-5/qset.html
[assignable data type]: http://doc.qt.io/qt-5/containers.html#assignable-data-type
[QWidget]: http://doc.qt.io/qt-5/qwidget.html
[qHash]: http://doc.qt.io/qt-5/qhash.html#qHash
[QHash]: http://doc.qt.io/qt-5/qhash.html#qhash
[Link 2]: http://doc.qt.io/qt-5/qhash.html
[QString]: http://doc.qt.io/qt-5/qstring.html
[Techie 1]: http://techieliang.com