Sort pair only on seam value

src/seam-carving.cpp

@@ -79,7 +79,8 @@ std::vector<int> optimal_vertical_seams(std::vector<unsigned char> energy, int w
   for (auto j=0; j < width; j++) {
     seamEnds[j] = {dyn_energy[(height-1)*width+j], j};
   }
-  std::sort(seamEnds.begin(), seamEnds.end());
+  std::sort(seamEnds.begin(), seamEnds.end(),
+      [](std::pair<int, int> a, std::pair<int, int> b) {return a.first > b.first; });
   for (auto seam=0; seam < nbSeams; seam++) {
     result[height*(seam+1)-1] = seamEnds[seam].second;
   }