add example of Hash structure

trick/hash-structure.cpp

@@ -0,0 +1,46 @@
+#include <vector>
+#include <tuple>
+#include <unordered_set>
+template<typename T>
+struct VectorHash {
+    static void has_combine(size_t& seed, const T& v) {
+        seed ^= hash<T>{}(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+    }
+
+    size_t operator() (const std::vector<T>& vec) const {
+        size_t seed = 0;
+        for (const T& v : vec) {
+            has_combine(seed, v);
+        }
+        return seed;
+    }
+};
+
+struct TupleHash {
+    template<typename T>
+    static void hash_combine(size_t& seed, const T& v) {
+        seed ^= hash<T>{}(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+    }
+
+    template<typename Tuple, size_t Index = 0>
+    static void hash_tuple(size_t& seed, const Tuple& t) {
+        if constexpr (Index < tuple_size_v<Tuple>) {
+            hash_combine(seed, get<Index>(t));
+            hash_tuple<Tuple, Index + 1>(seed, t);
+        }
+    }
+
+    template<typename... Ts>
+    size_t operator()(const std::tuple<Ts...>& t) const {
+        size_t seed = 0;
+        hash_tuple(seed, t);
+        return seed;
+    }
+};
+
+
+int main() {
+    std::unordered_set<std::vector<int>, VectorHash<int>> hash_set1;
+    std::unordered_set<std::tuple<int, int, int>, TupleHash> hash_set2;
+    return 0;
+}