Poj1436Horizontally Visible Segments线段树

 

这题拆点搞。比如 [1,2] [3,4]  这两段，可以有 2.2之类的点能使一条线射穿它，但是2.2这种点整数线段上搞不出来，然后就把2*2=4 ，3*2=6；这样新的线段就可以覆盖到他穿到能与他直线相连的线段上，记录下，然后三个for 枚举答案。

#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|1

const 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;

}