1 files changed, 48 insertions, 0 deletions
diff --git a/include/gudhi_laplacian/sparse_row.hpp b/include/gudhi_laplacian/sparse_row.hpp
new file mode 100644
index 0000000..9896625
--- /dev/null
+++ b/include/gudhi_laplacian/sparse_row.hpp
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <vector>
+#include <algorithm>
+#include <utility>
+#include <type_traits>
+
+namespace Gudhi_laplacian
+{
+  template <typename T>
+  using Sparse_row = std::vector<std::pair<unsigned int, T> >;
+
+  template <typename T>
+  void compress_sparse_row(Sparse_row<T> & row)
+  {
+    static_assert(std::is_arithmetic<T>::value, "Only arithmetic types are supported.");
+    
+    Sparse_row<T> tmp(row); 
+    row.clear();
+    std::sort(tmp.begin(), tmp.end());
+    for (auto it = tmp.cbegin(); it != tmp.cend(); ++it)
+    {
+      if (row.empty())
+      {
+        if (it->second != T())
+        {
+          row.push_back(*it);
+        }
+      }
+      else if (it->first == row.back().first)
+      {
+        T x = row.back().second + it->second;
+        if (x == T())
+        {
+          row.pop_back();
+        }
+        else
+        {
+          row.back().second = x;
+        }
+      }
+      else if (it->second != T())
+      {
+        row.push_back(*it); 
+      }
+    }
+  }
+}