# HG changeset patch
# User Peter Kovacs <kpeter@inf.elte.hu>
# Date 1254218582 -7200
# Node ID 5764dd9b6e184b4789131f58ec8cbec9bb1ff989
# Parent  eff1caf6d32e2d57692d0b9397e611dac1324f0c
Add a new build() function to StaticDigraph (#68)

This function builds the digraph from an arc list that
contains pairs of integer indices from the range [0..n-1].
It is useful in the cases when you would like to build a
StaticDigraph from scratch, i.e. you do not want to build
another digraph that can be copied using the other build()
function.

diff -r eff1caf6d32e -r 5764dd9b6e18 lemon/static_graph.h
--- a/lemon/static_graph.h	Tue Sep 29 10:39:20 2009 +0200
+++ b/lemon/static_graph.h	Tue Sep 29 12:03:02 2009 +0200
@@ -197,6 +197,47 @@
       }
       node_first_out[node_num] = arc_num;
     }
+    
+    template <typename ArcListIterator>
+    void build(int n, ArcListIterator first, ArcListIterator last) {
+      built = true;
+
+      node_num = n;
+      arc_num = std::distance(first, last);
+
+      node_first_out = new int[node_num + 1];
+      node_first_in = new int[node_num];
+
+      arc_source = new int[arc_num];
+      arc_target = new int[arc_num];
+      arc_next_out = new int[arc_num];
+      arc_next_in = new int[arc_num];
+      
+      for (int i = 0; i != node_num; ++i) {
+        node_first_in[i] = -1;
+      }      
+      
+      int arc_index = 0;
+      for (int i = 0; i != node_num; ++i) {
+        node_first_out[i] = arc_index;
+        for ( ; first != last && (*first).first == i; ++first) {
+          int j = (*first).second;
+          LEMON_ASSERT(j >= 0 && j < node_num,
+            "Wrong arc list for StaticDigraph::build()");
+          arc_source[arc_index] = i;
+          arc_target[arc_index] = j;
+          arc_next_in[arc_index] = node_first_in[j];
+          node_first_in[j] = arc_index;
+          arc_next_out[arc_index] = arc_index + 1;
+          ++arc_index;
+        }
+        if (arc_index > node_first_out[i])
+          arc_next_out[arc_index - 1] = -1;
+      }
+      LEMON_ASSERT(first == last,
+        "Wrong arc list for StaticDigraph::build()");
+      node_first_out[node_num] = arc_num;
+    }
 
   protected:
 
@@ -328,6 +369,44 @@
       Parent::build(digraph, nodeRef, arcRef);
     }
   
+    /// \brief Build the digraph from an arc list.
+    ///
+    /// This function builds the digraph from the given arc list.
+    /// It can be called more than once, but in such case, the whole
+    /// structure and all maps will be cleared and rebuilt.
+    ///
+    /// The list of the arcs must be given in the range <tt>[begin, end)</tt>
+    /// specified by STL compatible itartors whose \c value_type must be
+    /// <tt>std::pair<int,int></tt>.
+    /// Each arc must be specified by a pair of integer indices
+    /// from the range <tt>[0..n-1]</tt>. <i>The pairs must be in a
+    /// non-decreasing order with respect to their first values.</i>
+    /// If the k-th pair in the list is <tt>(i,j)</tt>, then
+    /// <tt>arc(k-1)</tt> will connect <tt>node(i)</tt> to <tt>node(j)</tt>.
+    ///
+    /// \param n The number of nodes.
+    /// \param begin An iterator pointing to the beginning of the arc list.
+    /// \param end An iterator pointing to the end of the arc list.
+    ///
+    /// For example, a simple digraph can be constructed like this.
+    /// \code
+    ///   std::vector<std::pair<int,int> > arcs;
+    ///   arcs.push_back(std::make_pair(0,1));
+    ///   arcs.push_back(std::make_pair(0,2));
+    ///   arcs.push_back(std::make_pair(1,3));
+    ///   arcs.push_back(std::make_pair(1,2));
+    ///   arcs.push_back(std::make_pair(3,0));
+    ///   StaticDigraph gr;
+    ///   gr.build(4, arcs.begin(), arcs.end());
+    /// \endcode
+    template <typename ArcListIterator>
+    void build(int n, ArcListIterator begin, ArcListIterator end) {
+      if (built) Parent::clear();
+      StaticDigraphBase::build(n, begin, end);
+      notifier(Node()).build();
+      notifier(Arc()).build();
+    }
+
     /// \brief Clear the digraph.
     ///
     /// This function erases all nodes and arcs from the digraph.
diff -r eff1caf6d32e -r 5764dd9b6e18 test/digraph_test.cc
--- a/test/digraph_test.cc	Tue Sep 29 10:39:20 2009 +0200
+++ b/test/digraph_test.cc	Tue Sep 29 12:03:02 2009 +0200
@@ -441,6 +441,38 @@
 
   checkGraphConArcList(G, 4);
 
+  std::vector<std::pair<int,int> > arcs;
+  arcs.push_back(std::make_pair(0,1));
+  arcs.push_back(std::make_pair(0,2));
+  arcs.push_back(std::make_pair(1,3));
+  arcs.push_back(std::make_pair(1,2));
+  arcs.push_back(std::make_pair(3,0));
+  arcs.push_back(std::make_pair(3,3));
+  arcs.push_back(std::make_pair(4,2));
+  arcs.push_back(std::make_pair(4,3));
+  arcs.push_back(std::make_pair(4,1));
+
+  G.build(6, arcs.begin(), arcs.end());
+  
+  checkGraphNodeList(G, 6);
+  checkGraphArcList(G, 9);
+
+  checkGraphOutArcList(G, G.node(0), 2);
+  checkGraphOutArcList(G, G.node(1), 2);
+  checkGraphOutArcList(G, G.node(2), 0);
+  checkGraphOutArcList(G, G.node(3), 2);
+  checkGraphOutArcList(G, G.node(4), 3);
+  checkGraphOutArcList(G, G.node(5), 0);
+
+  checkGraphInArcList(G, G.node(0), 1);
+  checkGraphInArcList(G, G.node(1), 2);
+  checkGraphInArcList(G, G.node(2), 3);
+  checkGraphInArcList(G, G.node(3), 3);
+  checkGraphInArcList(G, G.node(4), 0);
+  checkGraphInArcList(G, G.node(5), 0);
+
+  checkGraphConArcList(G, 9);
+
   checkNodeIds(G);
   checkArcIds(G);
   checkGraphNodeMap(G);