O(n^2) to O(n) optimization in QTreeWidget::selectedItems()

As we need to ensure that there will be no duplicates in the list
returned by QTreeWidget::selectedItems() (see commit
ea75d434e40100a9abf56195b646a8efdf3c1288), we now use a QSet to ensure
unicity while keeping the same order as before.

Reviewed-by: Olivier
Task-number: QTBUG-9485

1 files changed, 5 insertions, 1 deletions

diff --git a/src/gui/itemviews/qtreewidget.cpp b/src/gui/itemviews/qtreewidget.cpp
index 19ed10b..4c80325 100644
--- a/src/gui/itemviews/qtreewidget.cpp
+++ b/src/gui/itemviews/qtreewidget.cpp
@@ -3039,10 +3039,14 @@ QList<QTreeWidgetItem*> QTreeWidget::selectedItems() const
     Q_D(const QTreeWidget);
     QModelIndexList indexes = selectionModel()->selectedIndexes();
     QList<QTreeWidgetItem*> items;
+    items.reserve(indexes.count());
+    QSet<QTreeWidgetItem *> seen;
+    seen.reserve(indexes.count());
     for (int i = 0; i < indexes.count(); ++i) {
         QTreeWidgetItem *item = d->item(indexes.at(i));
-        if (isItemHidden(item) || items.contains(item)) // ### slow, optimize later
+        if (isItemHidden(item) || seen.contains(item))
             continue;
+        seen.insert(item);
         items.append(item);
     }
     return items;