use robin-hood-hashing

Author: wx257osn2

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "cpp/external_projects/robin-hood-hashing"]
+	path = cpp/external_projects/robin-hood-hashing
+	url = https://github.com/martinus/robin-hood-hashing

cpp/Makefile

@@ -4,4 +4,4 @@ clean:
 	rm main
 
 main: src/main.cpp
-	clang++ -std=c++17 -O3 -Wall -Wextra -pedantic-errors -march=native -mtune=native -o main src/main.cpp
+	clang++ -std=c++17 -O3 -Wall -Wextra -pedantic-errors -march=native -mtune=native -I external_projects/robin-hood-hashing/src/include -o main src/main.cpp

cpp/external_projects/robin-hood-hashing

@@ -6,6 +6,7 @@
 #include<queue>
 #include<cstdint>
 #include<limits>
+#include"robin_hood.h"
 
 using NodeId = int;
 using NodeIndex = int;
@@ -17,7 +18,7 @@ constexpr int DISTANCE_MULTIPLE = 100;
 bool is_debug = false;
 
 struct G {
-  std::unordered_map<NodeId,NodeIndex> id2idx;
+  robin_hood::unordered_map<NodeId,NodeIndex> id2idx;
   std::vector<NodeId> idx2id = {0};
   NodeIndex idx = 1;
   std::vector<std::vector<Edge>> edge = {std::vector<Edge>()};