poj1151Atlantis扫描线

　　第一道扫描线。

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>

using namespace std;

const int maxn = 4004;

double hash[maxn << 2];

int color[maxn << 2];

double sum[maxn << 2];

#define lson l,mid,rt<<1

#define rson mid+1,r,rt<<1|1



struct Node

{

    int add; double l; double r; double h;

}node[maxn << 2];



int cmp(const Node&a, const Node &b)

{

    return a.h<b.h;

}



void up(int l, int r, int rt)

{

    if (color[rt]>0) sum[rt] = hash[r + 1] - hash[l];  //第 l个线段到 第r个线段的长度 = 第r+1个点与第l个点的距离

    //else if (l == r) sum[rt] = 0;

    else sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];

}



void update(int L, int R, int add, int l, int r, int rt)

{

    if (L <= l&&r <= R){

        color[rt] += add;

        up(l, r, rt); return;

    }

    int mid = (l + r) >> 1;

    if (L <= mid) update(L, R, add, lson);

    if (R > mid) update(L, R, add, rson);

    up(l, r, rt);

}



int Bin(double key, double a[], int len)//  离散

{

    int l = 0; int r = len - 1;

    while (l <= r){

        int mid = (l + r) >> 1;

        if (a[mid] == key) return mid;

        if (a[mid] < key) l = mid + 1;

        else r = mid - 1;

    }

    return -1;

}



int main()

{

    int n;

    double a, b, c, d;

    int gg = 0;

    while (cin >> n, n){

        int m = 0;

        for (int i = 0; i < n; i++){

            cin >> a >> b >> c >> d;

            hash[m] = a;

            node[m].l = a; node[m].r = c; node[m].h = b; node[m++].add = 1;

            hash[m] = c;

            node[m].l = a; node[m].r = c; node[m].h = d; node[m++].add = -1;

        }

        int k = 0;

        sort(hash, hash + m);

        sort(node, node + m, cmp);

        k++;

        for (int i = 1; i<m; i++)

        if (hash[i] != hash[i - 1]) hash[k++] = hash[i];

        double ret = 0;

        for (int i = 0; i < m; i++){// 对最后一跟线扫完以后，sum与 color 都被清0了。 若是想手动初始化，就把 i<m  改为 i<m-1

            int L = Bin(node[i].l, hash, k);

            int R = Bin(node[i].r, hash, k) - 1;//点变线段 比如 1(1) 2 (2) 3 (3) 4

            update(L, R, node[i].add, 0, k - 1, 1);

            ret += sum[1] * (node[i + 1].h - node[i].h);

        }

        printf("Test case #%d\n", ++gg);

        printf("Total explored area: %.2f\n", ret);

        cout << endl;

    }

    return 0;

}