安全的哈希
安全的哈希
代码如下
const int maxn = 2e5 + 5;
struct custom_hash
{
static uint64_t splitmix64(uint64_t x)
{
x ^= x << 13;
x ^= x >> 7;
x ^= x << 17;
return x;
}
size_t operator () (uint64_t x) const
{
static const uint64_t FIXED_RANDOM = std::chrono::steady_clock::now().time_since_epoch().count(); // 时间戳
return splitmix64(x + FIXED_RANDOM);
}
};
std::unordered_map<uint64_t, int, custom_hash> mp;