Poj1436horizontally visible segments line segment tree

#include <cstdio>#include <cstring>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>#include<math.h>using namespace std;#define lson l,mid,rt<<1#define rson mid+1,r,rt<<1|1const int maxn = 8000 + 10;bool Hash[maxn][maxn];struct Node{    int a; int b; int c;}node[maxn];int color[maxn * 10];int cmp(const Node &a, const Node &b){    return a.c < b.c;}void down(int rt){    if (~color[rt]){        color[rt << 1] = color[rt << 1 | 1] = color[rt];        color[rt] = -1;    }}void build(int l, int r, int rt){    color[rt] = -1;    if (l == r) return;    int mid = (l + r) >> 1;    build(lson);    build(rson);}void update(int L, int R, int add, int l, int r, int rt){    if (L <= l&&r <= R){        color[rt] = add; return;    }    down(rt);    int mid = (l + r) >> 1;    if (L <= mid) update(L, R, add, lson);    if (R > mid) update(L, R, add, rson);}void ask(int L, int R, int add, int l, int r, int rt){    if (~color[rt]){        Hash[add][color[rt]] = Hash[color[rt]][add] = add;        return;    }    if (l == r) return;    int mid = (l + r) >> 1;    if (L <= mid) ask(L, R, add, lson);    if (R > mid) ask(L, R, add, rson);}int main(){    int Icase, n;    cin >> Icase;    while (Icase--){        cin >> n;        int ans = 0;        int Max = 0;        memset(Hash, 0, sizeof(Hash));        for (int i = 0; i < n; i++){            int a; int b; int c;            scanf("%d%d%d", &a, &b, &c);            node[i].a = a * 2; node[i].b = b * 2; node[i].c = c;            if (node[i].b>Max) Max = node[i].b;        }        sort(node, node + n, cmp);        build(0, Max, 1);        for (int i = 0; i < n; i++){            ask(node[i].a, node[i].b, i, 0, Max, 1);            update(node[i].a, node[i].b, i, 0, Max, 1);        }        for (int i = 0; i < n; i++){            for (int j = i + 1; j < n; j++){                if (!Hash[i][j]) continue;                for (int k = j + 1; k < n; k++){                    if (Hash[i][k] && Hash[j][k])ans++;                }            }        }        cout << ans << endl;    }    return 0;}