Create a separate class for spanning tree

Remarks:

1. Templates should be in header files only

2. Should pass in svector<_> instead of returning a local one

src/smt/spanning_tree_base.h

@@ -0,0 +1,71 @@
+/*++
+Copyright (c) 2013 Microsoft Corporation
+
+Module Name:
+
+    spanning_tree_base.h
+
+Abstract:
+
+    Represent spanning trees with needed operations for Network Simplex
+
+Author:
+
+    Anh-Dung Phan (t-anphan) 2013-11-06
+
+Notes:
+   
+--*/
+
+#ifndef _SPANNING_TREE_BASE_H_
+#define _SPANNING_TREE_BASE_H_
+
+#include "util.h"
+#include "vector.h"
+
+namespace smt {
+    typedef int node;
+
+    template<typename TV>
+    inline std::string pp_vector(std::string const & label, TV v, bool has_header = false) {
+        std::ostringstream oss;
+        if (has_header) {
+            oss << "Index ";
+            for (unsigned i = 0; i < v.size(); ++i) {
+                oss << i << " ";
+            }
+            oss << std::endl;
+        }
+        oss << label << " ";
+        for (unsigned i = 0; i < v.size(); ++i) {
+            oss << v[i] << " ";
+        }
+        oss << std::endl;
+        return oss.str();
+    }
+
+    class spanning_tree_base {        
+    public:
+        spanning_tree_base() {};
+        virtual ~spanning_tree_base() {};
+
+        virtual void initialize(svector<bool> const & upwards, int num_nodes) = 0;
+        /**
+            \brief Get all descendants of a node including itself
+        */
+        virtual void get_descendants(node start, svector<node>& descendants) = 0;
+        /**
+            \brief Get all ancestors of a node including itself
+        */
+        virtual void get_ancestors(node start, svector<node>& ancestors) = 0;
+        virtual node get_common_ancestor(node u, node v) = 0;
+        virtual void update(node p, node q, node u, node v) = 0;
+        virtual bool check_well_formed() = 0;
+
+        // TODO: remove these two unnatural functions
+        virtual bool get_arc_direction(node start) const = 0;
+        virtual node get_parent(node start) = 0;
+    };
+}
+
+#endif