P

题意：rt 求面积......不计算重复面积(废话。。)hdu1255 的弱化版，应该先做这道题在做那道题的。

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---

#include<stdio.h>
#include<algorithm>
#include<math.h>
using namespace std;

#define Lson r<<1
#define Rson r<<1|1

const int MAXN = 1e5+5;

struct segmentTree
{///cover记录本区间是否被覆盖,len记录被覆盖的长度
    int L, R, cover;
    double len;
    int mid(){return (L+R)>>1;}
}a[MAXN<<2];
double Hash[MAXN]; int nh;///记录离散化后的数据
///记录矩形的y边，dir等1表示左边， -1表示右边
struct Edge{double x, y1, y2; int dir;}e[MAXN];
bool cmp(Edge n1, Edge n2)
{///把边按照x从小往大排序
    return n1.x < n2.x;
}
///求y边的长度
double FindEgeLen(int y1, int y2)
{///y1 < y2
    return Hash[y2] - Hash[y1];
}
void BuildSegTree(int r, int L, int R)
{///建立紧密线段树
    a[r].L = L, a[r].R = R;
    a[r].len = a[r].cover = 0;

    if(L == R-1)return ;

    BuildSegTree(Lson, L, a[r].mid());
    BuildSegTree(Rson, a[r].mid(), R);
}
void PushUp(int r)
{
    if(a[r].cover)
        a[r].len = FindEgeLen( a[r].L, a[r].R );
    else if(a[r].L == a[r].R-1)
        a[r].len = 0;
    else
        a[r].len = a[Lson].len + a[Rson].len;
}
void UpData(int r, int L, int R, int dir)
{
    if(a[r].L == L && a[r].R == R)
    {
        a[r].cover += dir;
        PushUp(r);

        return ;
    }

    if(R <= a[r].mid())
        UpData(Lson, L, R, dir);
    else if(L >= a[r].mid())
        UpData(Rson, L, R, dir);
    else
    {
        UpData(Lson, L, a[r].mid(), dir);
        UpData(Rson, a[r].mid(), R, dir);
    }

    PushUp(r);
}

int main()
{
    int i, N, t=1;

    while(scanf("%d", &N), N)
    {
        double x1, x2, y1, y2, area=0; int k = 0; nh = 0;

        for(i=0; i<N; i++)
        {
            scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);
            e[k].x=x1, e[k].y1=y1, e[k].y2=y2, e[k++].dir=1;
            e[k].x=x2, e[k].y1=y1, e[k].y2=y2, e[k++].dir=-1;
            Hash[nh++] = y1, Hash[nh++] = y2;
        }

        sort(Hash, Hash+nh);
        nh = unique(Hash, Hash+nh)-Hash;

        BuildSegTree(1, 0, nh-1);

        sort(e, e+k, cmp);

        for(i=0; i<k-1; i++)
        {
            int L = lower_bound(Hash, Hash+nh, e[i].y1)-Hash;
            int R = lower_bound(Hash, Hash+nh, e[i].y2)-Hash;

            UpData(1, L, R, e[i].dir);

            area += a[1].len * (e[i+1].x - e[i].x);
        }

        printf("Test case #%d
", t++);
        printf("Total explored area: %.2f

", area);
    }

    return 0;
}