ref argmax，fix <vect>

src/layer/topk.cpp

@@ -13,8 +13,7 @@
 // specific language governing permissions and limitations under the License.
 
 #include "topk.h"
-#include <vector>
-#include <algorithm>
+#include <functional>
 
 namespace ncnn {
 
@@ -52,40 +51,25 @@ int TopK::forward(const Mat& bottom_blob, Mat& top_blob, const Option& opt) cons
     }
 
     // [](const std::pair<float, int>& a, const std::pair<float, int>& b) {return a.first > b.first;}); // fix Lambda with lower version of C++
-    struct CompareGreater
-    {
-        bool operator()(const std::pair<float, int>& a, const std::pair<float, int>& b) const
-        {
-            return a.first > b.first;
-        }
-    };
-
-    struct CompareLess
-    {
-        bool operator()(const std::pair<float, int>& a, const std::pair<float, int>& b) const
-        {
-            return a.first < b.first;
-        }
-    };
 
     if (largest == 1)
     {
-        std::partial_sort(vec.begin(), vec.begin() + k_, vec.end(), CompareGreater());
+        std::partial_sort(vec.begin(), vec.begin() + k_, vec.end(), std::greater<std::pair<float, int> >());
     }
     else
     {
-        std::partial_sort(vec.begin(), vec.begin() + k_, vec.end(), CompareLess());
+        std::partial_sort(vec.begin(), vec.begin() + k_, vec.end(), std::less<std::pair<float, int> >());
     }
 
     if (sorted)
     {
         if (largest == 1)
         {
-            std::sort(vec.begin(), vec.begin() + k_, CompareGreater());
+            std::sort(vec.begin(), vec.begin() + k_, std::greater<std::pair<float, int> >());
         }
         else
         {
-            std::sort(vec.begin(), vec.begin() + k_, CompareLess());
+            std::sort(vec.begin(), vec.begin() + k_, std::less<std::pair<float, int> >());
         }
     }