手写哈希

struct my_hash{
    //unordered_map long long , int
    static const int BUFF=524287;
    static const int EDGE=200010;
    int fi[BUFF+1],k,ne[EDGE];
    long long b[EDGE];
    int c[EDGE];
    __attribute__((always_inline)) int& operator [](long long x){
        if (fi[x&BUFF]){
            for (int j=fi[x&BUFF]; j; j=ne[j])
                if (b[j]==x) return c[j];
            ne[++k]=fi[x&BUFF];
            b[fi[x&BUFF]=k]=x;
            return c[k];
        }
        ne[++k]=0;
        b[fi[x&BUFF]=k]=x;
        return c[k];
    }
    void clear(){
        memset(c+1,0,k*sizeof(*c));
        k=0;
        memset(fi,0,(BUFF+1)*sizeof(*fi));
    }
}mpp;

struct my_hash{
    //stable in linux but slow
    static const int BUFF=524287; 
    int fi[BUFF+1];
    vector<int> ne,c;
    vector<long long> b;
    my_hash(){
        ne.emplace_back(0);
        c.emplace_back(0);
        b.emplace_back(0);
    };
    __attribute__((always_inline)) int& operator [](long long x){
        if (fi[x&BUFF]){
            for (int j=fi[x&BUFF]; j; j=ne[j])
                if (b[j]==x) return c[j];
            fi[x&BUFF]=ne.size();
            ne.emplace_back(fi[x&BUFF]);
            b.emplace_back(x);
            c.emplace_back(0);
            return c.back();
        }
        fi[x&BUFF]=ne.size();
        ne.emplace_back(0);
        b.emplace_back(x);
        c.emplace_back(0);
        return c.back();
    }
    void clear(){
        ne.clear();
        b.clear();
        c.clear();
        memset(fi,0,(BUFF+1)*sizeof(*fi));
    }
}mpp;

template<class T1,class T2>
struct my_hash{
    static const int BUFF=524287;
    static const int EDGE=200010;
    int fi[BUFF+1],k,ne[EDGE];//wei chu shi hua
    T1 b[EDGE];
    T2 c[EDGE];
    __attribute__((always_inline)) T2& operator [](const T1 &x){
        int temp=x&BUFF;
        if (fi[temp]){
            for (int j=fi[temp]; j; j=ne[j])
                if (b[j]==x) return c[j];
            ne[++k]=fi[temp];
            b[fi[temp]=k]=x;
            return c[k]=*(new T2());
        }
　　　　　　ne[++k]=0;
        b[fi[temp]=k]=x;
        return c[k]=*(new T2());
    }
    void clear(){
        k=0;
        memset(fi,0,(BUFF+1)*sizeof(*fi));
    }
};

 内存不泄漏版

#include <bits/stdc++.h>
using namespace std;
template<class T1,class T2>
struct my_hash{
    static const int BUFF=10503465;
    static const int EDGE=1000010;
    int fi[BUFF+1],k,ne[EDGE];//wei chu shi hua
    T1 b[EDGE];
    T2 c[EDGE];
    __attribute__((always_inline)) T2& operator [](const T1 &x){
        int temp=x&BUFF;
        if (fi[temp]){
            for (int j=fi[temp]; j; j=ne[j])
                if (b[j]==x) return c[j];
            ne[++k]=fi[temp];
            b[fi[temp]=k]=x;
            T2 *p=new T2();
            c[k]=*p;
            delete p;
            return c[k];
        }
　　　　　ne[++k]=0;
        b[fi[temp]=k]=x;
        T2 *p=new T2();
        c[k]=*p;
        delete p;
        return c[k];
    }
    void clear(){
        k=0;
        memset(fi,0,(BUFF+1)*sizeof(*fi));
    }
};

 另一种版本

struct my_hash{
    static const int BUFF=8388607;
    static const int EDGE=10000010;
    int fi[BUFF+1],k,ne[EDGE];//wei chu shi hua
    T1 b[EDGE];
    T2 c[EDGE];
    __attribute__((always_inline)) T2& operator [](const T1 &x){
        int temp=x&BUFF;
        if (fi[temp]){
            for (int j=fi[temp]; j; j=ne[j])
                if (b[j]==x) return c[j];
            ne[++k]=fi[temp];
            b[fi[temp]=k]=x;
            return c[k];
        }
　　　　  ne[++k]=0;
        b[fi[temp]=k]=x;
        return c[k];
    }
    void clear(){
        for (int i=1; i<=k; ++i) c[i]=T2();
        k=0;
        memset(fi,0,(BUFF+1)*sizeof(*fi));
    }
};

特化版比模板的快1/4左右，EDGE是总访问数。