count(); return splitmix64(x + FIXED_RANDOM); } }; unordered_map<int, int,custom_hash> mp; mp.reserve(1024); mp.max_load_factor(0.25); 用gp_hash_table 变得更快 参考文章:浅谈pb_ds 库及其在 OI/其他算竞中的应用gp_hash_table 使用探测法,常数小,加入自定义hash后依然很快。综合最优...
std::size_t operator()(const std::string& key) const { std::size_t hash = 0; for (char c : key) { hash = hash * 31 + c; // 简单的哈希计算方式 } return hash; } }; int main() { std::unordered_map<std::string, int, CustomHash> myMap; myMap["apple"] = 1; myMap[...
};unordered_map<longlong,int, custom_hash> safe_map; gp_hash_table<longlong,int, custom_hash> safe_hash_table; referto:referto:
不同的是unordered_map不会根据key的大小进行排序, 存储时是根据key的hash值判断元素是否相同,即unordered_map内部元素是无序的,而map中的元素是按照二叉搜索树存储,进行中序遍历会得到有序遍历。 所以使用时map的key需要定义operator<。而unordered_map需要定义hash_value函数并且重载operator==。但是很多系统内置的数据...
貌似听说会有卡unordered_map的,有巨佬给出了解决方案。基于一个随机时间的种子再配上一些奇怪的数字让你的程序抖动得更强。 structcustom_hash{staticuint64_tsplitmix64(uint64_tx){ x +=0x9e3779b97f4a7c15; x = (x ^ (x >>30)) *0xbf58476d1ce4e5b9; ...
count(); return splitmix64(x + FIXED_RANDOM); } }; unordered_map<int, int, custom_hash> mp; 其主要思路是通过给与哈希函数随机性,以防止被特别设计的数据制造出大量的哈希碰撞。自定义哈希函数后,就可以愉快的AC掉这道题啦。 结论 在数据量能够满足O(nlogn)要求的情况下,尽量使用二分查找的方法,...
//std::unordered_map<const i_b*, c*, std::hash<const i_b*>, std::equal_to<const i_b*>> Bs_to_Cs_{};//working fine, but no custom allocator std::unordered_map<const i_b*, c*, std::hash<const i_b*>, std::equal_to<const i_b*>, tlsf_allocator::allocator_for<std:...
To do this we can write our own custom hash function which we give to the unordered_map (or gp_hash_table, etc.). The standard hash function looks something like this: struct custom_hash { size_t operator()(uint64_t x) const { return x; } }; However as we mentioned, any ...
But one cannot say for sure until they in fact look into the code. Personally I use Map (most of the Times) Situation 1 : Once I used Unordered Map(With Custom Hash) It gave me TLE I tried multiple Types of hashes Still It Didn't Worked. With Map It got Accepted....
end()); // Option 1 for a constructor with a custom Key type // Define the KeyHash and KeyEqual structs and use them in the template std::unordered_map<Key, std::string, KeyHash, KeyEqual> m6 = { {{"John", "Doe"}, "example"}, {{"Mary", "Sue"}, "another"} }; // ...