unordered_map 的火车头

#include <functional>
template <typename T>
inline void hash_combine(std::size_t &seed, const T &val) {
    seed ^= std::hash<T>()(val) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}
template <typename T> inline void hash_val(std::size_t &seed, const T &val) {
    hash_combine(seed, val);
}
template <typename T, typename... Types>
inline void hash_val(std::size_t &seed, const T &val, const Types &... args) {
    hash_combine(seed, val);
    hash_val(seed, args...);
}

template <typename... Types>
inline std::size_t hash_val(const Types &... args) {
    std::size_t seed = 0;
    hash_val(seed, args...);
    return seed;
}

struct pair_hash {
    template <class T1, class T2>
    std::size_t operator()(const std::pair<T1, T2> &p) const {
        return hash_val(p.first, p.second);
    }
};

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    unordered_map<pair<ll, ll>, ll, pair_hash> slopeCount;
    unordered_set<pair<ll, ll>, pair_hash> seen;
    return 0;
}

标签：std,map,火车头,hash,val,seed,const,unordered,size
来源： https://www.cnblogs.com/LH2000/p/14407030.html