NEUOJ 1702：撩妹全靠魅力值（CDQ分治三维偏序）

http://acm.neu.edu.cn/hustoj/problem.php?id=1702

思路：三维偏序模板题，用CDQ分治+树状数组或者树套树。对于三元组（x，y，z），先对x进行排序，然后对x进行CDQ分治降维，在分治的区间对y进行排序，用树状数组维护z。

还不太理解CDQ分治。等待UPDATE。

 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <cstdlib>
 #include <algorithm>
 #include <string>
 #include <iostream>
 #include <stack>
 #include <map>
 #include <queue>
 #include <set>
 using namespace std;
 typedef long long LL;
 #define N 100010
 #define INF 0x3f3f3f3f
 struct node {
     int id, x, y, z;
     node () {}
     node (int x, int y, int z, int id) : x(x), y(y), z(z), id(id) {}
     bool operator == (const node &A) const {
         return (x == A.x && y == A.y && z == A.z);
     }
 } p[N];

 int gap, same[N], bit[N], ans[N];

 bool cmpx(const node &a, const node &b) {
     if(a.x != b.x) return a.x < b.x;
     if(a.y != b.y) return a.y < b.y;
     return a.z < b.z;
 }

 bool cmpy(const node &a, const node &b) {
     if(a.y != b.y) return a.y < b.y;
     if(a.x != b.x) return a.x < b.x;
     return a.z < b.z;
 }

 bool cmpid(const node &a, const node &b) { return a.id < b.id; }

 int lowbit(int x) { return x & (-x); }

 void update(int x, int val) {
     while(x <= gap) {
         bit[x] += val;
         x += lowbit(x);
     }
 }

 int query(int x) {
     int ans = ;
     while(x) {
         ans += bit[x];
         x -= lowbit(x);
     }
     return ans;
 }

 void CDQ(int l, int r) {
     if(l == r) return ;
     int mid = (l + r) >> ;
     CDQ(l, mid); CDQ(mid + , r);
     sort(p + l, p + r + , cmpy);
     for(int i = l; i <= r; i++)
         if(p[i].x <= mid) update(p[i].z, );
         else ans[p[i].id] += query(p[i].z);
     for(int i = l; i <= r; i++)
         if(p[i].x <= mid) update(p[i].z, -);
 }

 int main()
 {
     int t;
     scanf("%d", &t);
     while(t--) {
         int n, a, b, c;
         scanf("%d", &n);
         gap = ;
         for(int i = ; i <= n; i++) {
             scanf("%d%d%d", &a, &b, &c);
             p[i] = node(a, b, c, i);
             if(c > gap) gap = c;
         }
         sort(p + , p +  + n, cmpx);
         memset(same, , sizeof(same));
         for(int i = ; i <= n; ) {
             int j = i + ;
             while(p[i] == p[j] && j <= n) j++;
             while(i < j) same[p[i++].id] = p[j-].id;
         }
         memset(bit, , sizeof(bit));
         memset(ans, , sizeof(ans));
         for(int i = ; i <= n; i++) p[i].x = i;
         CDQ(, n);
         sort(p + , p +  + n, cmpid);
         for(int i = ; i <= n; i++)
             printf("%d\n", ans[same[p[i].id]]);
     }
     return ;
 }