四维偏序

CDQ套CDQ或者CDQ套树套树
前者快于后者然而我写了后者

# include <stdio.h># include <stdlib.h># include <iostream># include <algorithm># include <string.h># define IL inline# define RG register# define Fill(a, b) memset(a, b, sizeof(a))using namespace std;typedef long long ll;IL ll Read(){    RG char c = getchar(); RG ll x = 0, z = 1;    for(; c < '0' || c > '9'; c = getchar()) z = c == '-' ? -1 : 1;    for(; c >= '0' && c <= '9'; c = getchar()) x = (x << 1) + (x << 3) + c - '0';    return x * z;}const int MAXN(50010);int n, k, ans, cnt;struct Point{    int a, b, c, d;    IL bool operator <(RG Point B) const{        if(a != B.a) return a < B.a;        if(b != B.b) return b < B.b;        if(c != B.c) return c < B.c;        return d < B.d;    }} p[MAXN];struct Treap{    int key, fix, size, num;    Treap *ch[2];    IL Treap(int x){          num = size = 1;          fix = rand();          key = x;          ch[0] = ch[1] = NULL;      }} *root[MAXN << 1];IL void Updata(Treap *x){    x -> size = x -> num;    if(x -> ch[0] != NULL) x -> size += x -> ch[0] -> size;    if(x -> ch[1] != NULL) x -> size += x -> ch[1] -> size;}IL void Rot(Treap *&x, int c){    Treap *y = x -> ch[!c];    x -> ch[!c] = y -> ch[c];    y -> ch[c] = x;    Updata(x); Updata(y);    x = y;}IL void Insert(Treap *&x, int val){    if(x == NULL) x = new Treap(val);    else if(x -> key == val) x -> num++;    else{        int c = val > x -> key;        Insert(x -> ch[c], val);        if(x -> ch[c] -> fix > x -> fix)            Rot(x, c ^ 1);    }    Updata(x);}IL void Delete(Treap *&x, int val){    if(val == x -> key){        Treap *tmp = x;        if(x -> num > 1) x -> num--;        else if(x -> ch[0] == NULL){            x = x -> ch[1];            delete tmp;        }        else if(x -> ch[1] == NULL){            x = x -> ch[0];            delete tmp;        }        else{            int c = x -> ch[0] -> fix > x -> ch[1] -> fix;            Rot(x, c);            Delete(x -> ch[c], val);        }    }    else{        int c = val > x -> key;        Delete(x -> ch[c], val);    }    if(x != NULL) Updata(x);}IL void Rank(Treap *x, int val){    if(x == NULL) return;    if(val < x -> key) Rank(x -> ch[0], val);       else{        if(x -> ch[0] != NULL) cnt += x -> ch[0] -> size;        if(x -> key == val) return;        cnt += x -> num;        Rank(x -> ch[1], val);    }}IL void Add(RG int x, RG int y){  for(; x <= n; x += x & -x) Insert(root[x], y);  }IL int Query(RG int x, RG int y){  cnt = 0; for(; x; x -= x & -x) Rank(root[x], y); return cnt;  } IL void Del(RG int x, RG int y){  for(; x <= n; x += x & -x) Delete(root[x], y);  }IL void CDQ(RG int l, RG int r){    if(l == r) return;    RG int mid = (l + r) >> 1; CDQ(l, mid); CDQ(mid + 1, r);    sort(p + l, p + r + 1);//可以归并排序    for(RG int i = l; i <= r; i++)        if(p[i].d <= mid) Add(p[i].b, p[i].c);        else ans += Query(p[i].b, p[i].c);    for(RG int i = l; i <= r; i++)        if(p[i].d <= mid) Del(p[i].b, p[i].c);}int main(RG int argc, RG char* argv[]){    n = Read();    for(RG int i = 1; i <= n; i++) p[i].a = Read();    for(RG int i = 1; i <= n; i++) p[i].b = Read();    for(RG int i = 1; i <= n; i++) p[i].c = Read();    for(RG int i = 1; i <= n; i++) p[i].d = i;    CDQ(1, n);    printf("%d\n", ans);    return 0;}