https://gcc.gnu.org/g:2e27df6cbd05a3ee742434b7f50dbff5f363b487

commit r16-771-g2e27df6cbd05a3ee742434b7f50dbff5f363b487
Author: Xℹ Ruoyao <xry...@mengyan1223.wang>
Date:   Fri Jul 10 20:58:04 2020 +0800

    libstdc++: maintain subtree size in pb_ds binary search trees
    
    libstdc++-v3/ChangeLog:
    
            * include/ext/pb_ds/detail/rb_tree_map_/node.hpp
            (rb_tree_node_::size_type): New typedef.
            (rb_tree_node_::m_subtree_size): New field.
            * include/ext/pb_ds/detail/splay_tree_/node.hpp
            (splay_tree_node_::size_type): New typedef.
            (splay_tree_node_::m_subtree_size): New field.
            * include/ext/pb_ds/detail/bin_search_tree_/bin_search_tree_.hpp
            (PB_DS_BIN_TREE_NAME::update_subtree_size): Declare new member
            function.
            * include/ext/pb_ds/detail/bin_search_tree_/rotate_fn_imps.hpp
            (update_subtree_size): Define.
            (apply_update, update_to_top): Call update_subtree_size.

Diff:
---
 .../detail/bin_search_tree_/bin_search_tree_.hpp   |  3 +++
 .../detail/bin_search_tree_/rotate_fn_imps.hpp     | 31 +++++++++++++++++++---
 .../include/ext/pb_ds/detail/rb_tree_map_/node.hpp |  8 ++++++
 .../include/ext/pb_ds/detail/splay_tree_/node.hpp  |  8 ++++++
 4 files changed, 46 insertions(+), 4 deletions(-)

diff --git 
a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/bin_search_tree_.hpp 
b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/bin_search_tree_.hpp
index 6088709998a3..a8c73b55b89d 100644
--- 
a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/bin_search_tree_.hpp
+++ 
b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/bin_search_tree_.hpp
@@ -304,6 +304,9 @@ namespace __gnu_pbds
       inline void
       rotate_parent(node_pointer);
 
+      inline void
+      update_subtree_size(node_pointer);
+
       inline void
       apply_update(node_pointer, null_node_update_pointer);
 
diff --git 
a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/rotate_fn_imps.hpp 
b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/rotate_fn_imps.hpp
index 069b17f08de2..8cadce2349bd 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/rotate_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/rotate_fn_imps.hpp
@@ -122,8 +122,23 @@ rotate_parent(node_pointer p_nd)
 PB_DS_CLASS_T_DEC
 inline void
 PB_DS_CLASS_C_DEC::
-apply_update(node_pointer /*p_nd*/, null_node_update_pointer /*p_update*/)
-{ }
+update_subtree_size(node_pointer p_nd)
+{
+  size_type size = 1;
+  if (p_nd->m_p_left)
+    size += p_nd->m_p_left->m_subtree_size;
+  if (p_nd->m_p_right)
+    size += p_nd->m_p_right->m_subtree_size;
+  p_nd->m_subtree_size = size;
+}
+
+PB_DS_CLASS_T_DEC
+inline void
+PB_DS_CLASS_C_DEC::
+apply_update(node_pointer p_nd, null_node_update_pointer /*p_update*/)
+{
+  update_subtree_size(p_nd);
+}
 
 PB_DS_CLASS_T_DEC
 template<typename Node_Update_>
@@ -131,6 +146,7 @@ inline void
 PB_DS_CLASS_C_DEC::
 apply_update(node_pointer p_nd, Node_Update_*  /*p_update*/)
 {
+  update_subtree_size(p_nd);
   node_update::operator()(node_iterator(p_nd),
                          node_const_iterator(static_cast<node_pointer>(0)));
 }
@@ -152,7 +168,14 @@ update_to_top(node_pointer p_nd, Node_Update_* p_update)
 PB_DS_CLASS_T_DEC
 inline void
 PB_DS_CLASS_C_DEC::
-update_to_top(node_pointer /*p_nd*/, null_node_update_pointer /*p_update*/)
-{ }
+update_to_top(node_pointer p_nd, null_node_update_pointer /*p_update */)
+{
+  while (p_nd != m_p_head)
+    {
+      update_subtree_size(p_nd);
+
+      p_nd = p_nd->m_p_parent;
+    }
+}
 
 #endif
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/rb_tree_map_/node.hpp 
b/libstdc++-v3/include/ext/pb_ds/detail/rb_tree_map_/node.hpp
index f229be7342c6..3803ddb19c5d 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/rb_tree_map_/node.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/rb_tree_map_/node.hpp
@@ -58,6 +58,9 @@ namespace __gnu_pbds
       typedef typename rebind_traits<_Alloc, rb_tree_node_>::pointer
        node_pointer;
 
+      typedef typename rebind_traits<_Alloc, rb_tree_node_>::size_type
+       size_type;
+
       typedef typename rebind_traits<_Alloc, metadata_type>::reference
        metadata_reference;
 
@@ -88,6 +91,7 @@ namespace __gnu_pbds
       node_pointer     m_p_left;
       node_pointer     m_p_right;
       node_pointer     m_p_parent;
+      size_type        m_subtree_size;
       value_type       m_value;
       bool             m_red;
       metadata_type    m_metadata;
@@ -100,6 +104,9 @@ namespace __gnu_pbds
       typedef Value_Type               value_type;
       typedef null_type        metadata_type;
 
+      typedef typename rebind_traits<_Alloc, rb_tree_node_>::size_type
+       size_type;
+
       typedef typename rebind_traits<_Alloc, rb_tree_node_>::pointer
        node_pointer;
 
@@ -116,6 +123,7 @@ namespace __gnu_pbds
       node_pointer     m_p_left;
       node_pointer     m_p_right;
       node_pointer     m_p_parent;
+      size_type        m_subtree_size;
       value_type       m_value;
       bool             m_red;
     };
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/splay_tree_/node.hpp 
b/libstdc++-v3/include/ext/pb_ds/detail/splay_tree_/node.hpp
index 961afbe8664b..b5fbb500c8e0 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/splay_tree_/node.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/splay_tree_/node.hpp
@@ -56,6 +56,9 @@ namespace __gnu_pbds
       typedef typename rebind_traits<_Alloc, splay_tree_node_>::pointer
        node_pointer;
 
+      typedef typename rebind_traits<_Alloc, splay_tree_node_>::size_type
+       size_type;
+
       typedef typename rebind_traits<_Alloc, metadata_type>::reference
        metadata_reference;
 
@@ -85,6 +88,7 @@ namespace __gnu_pbds
       node_pointer m_p_left;
       node_pointer m_p_right;
       node_pointer m_p_parent;
+      size_type m_subtree_size;
       metadata_type m_metadata;
     };
 
@@ -98,6 +102,9 @@ namespace __gnu_pbds
       typedef typename rebind_traits<_Alloc, splay_tree_node_>::pointer
        node_pointer;
 
+      typedef typename rebind_traits<_Alloc, splay_tree_node_>::size_type
+       size_type;
+
       inline bool
       special() const
       { return m_special; }
@@ -111,6 +118,7 @@ namespace __gnu_pbds
       node_pointer m_p_left;
       node_pointer m_p_right;
       node_pointer m_p_parent;
+      size_type m_subtree_size;
       value_type m_value;
       bool m_special;
     };

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