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。
1 #include <cstdio> 2 #include <cstring> 3 #include <cmath> 4 #include <cstdlib> 5 #include <algorithm> 6 #include <string> 7 #include <iostream> 8 #include <stack> 9 #include <map> 10 #include <queue> 11 #include <set> 12 using namespace std; 13 typedef long long LL; 14 #define N 100010 15 #define INF 0x3f3f3f3f 16 struct node { 17 int id, x, y, z; 18 node () {} 19 node (int x, int y, int z, int id) : x(x), y(y), z(z), id(id) {} 20 bool operator == (const node &A) const { 21 return (x == A.x && y == A.y && z == A.z); 22 } 23 } p[N]; 24 25 int gap, same[N], bit[N], ans[N]; 26 27 bool cmpx(const node &a, const node &b) { 28 if(a.x != b.x) return a.x < b.x; 29 if(a.y != b.y) return a.y < b.y; 30 return a.z < b.z; 31 } 32 33 bool cmpy(const node &a, const node &b) { 34 if(a.y != b.y) return a.y < b.y; 35 if(a.x != b.x) return a.x < b.x; 36 return a.z < b.z; 37 } 38 39 bool cmpid(const node &a, const node &b) { return a.id < b.id; } 40 41 int lowbit(int x) { return x & (-x); } 42 43 void update(int x, int val) { 44 while(x <= gap) { 45 bit[x] += val; 46 x += lowbit(x); 47 } 48 } 49 50 int query(int x) { 51 int ans = 0; 52 while(x) { 53 ans += bit[x]; 54 x -= lowbit(x); 55 } 56 return ans; 57 } 58 59 void CDQ(int l, int r) { 60 if(l == r) return ; 61 int mid = (l + r) >> 1; 62 CDQ(l, mid); CDQ(mid + 1, r); 63 sort(p + l, p + r + 1, cmpy); 64 for(int i = l; i <= r; i++) 65 if(p[i].x <= mid) update(p[i].z, 1); 66 else ans[p[i].id] += query(p[i].z); 67 for(int i = l; i <= r; i++) 68 if(p[i].x <= mid) update(p[i].z, -1); 69 } 70 71 int main() 72 { 73 int t; 74 scanf("%d", &t); 75 while(t--) { 76 int n, a, b, c; 77 scanf("%d", &n); 78 gap = 0; 79 for(int i = 1; i <= n; i++) { 80 scanf("%d%d%d", &a, &b, &c); 81 p[i] = node(a, b, c, i); 82 if(c > gap) gap = c; 83 } 84 sort(p + 1, p + 1 + n, cmpx); 85 memset(same, 0, sizeof(same)); 86 for(int i = 1; i <= n; ) { 87 int j = i + 1; 88 while(p[i] == p[j] && j <= n) j++; 89 while(i < j) same[p[i++].id] = p[j-1].id; 90 } 91 memset(bit, 0, sizeof(bit)); 92 memset(ans, 0, sizeof(ans)); 93 for(int i = 1; i <= n; i++) p[i].x = i; 94 CDQ(1, n); 95 sort(p + 1, p + 1 + n, cmpid); 96 for(int i = 1; i <= n; i++) 97 printf("%d\n", ans[same[p[i].id]]); 98 } 99 return 0; 100 }
