面积

#include "stdio.h"#include "algorithm"using namespace std;const int maxn = 2010;int n;double y[maxn];struct node{    double x,y1,y2;    //x 边的位置  y边的区间大小     int f;                //f 标记 前边还是后边}Line[maxn];struct node1{    double y1,y2,inlen;    //  inlen线段被覆盖两次的长度    int ld,rd,c;                 // c为被覆盖次数}tree[maxn*4];bool cmp( node a,node b ){    return a.x < b.x;}void buildtree( int ld,int rd,int t)  // 建树{    tree[t].c = 0;      tree[t].inlen = 0;    tree[t].ld = ld;     tree[t].rd = rd;    tree[t].y1 = y[ld]; tree[t].y2 = y[rd];    if( ld+1 == rd )        return;    int mid = ( ld+rd )/2;    buildtree( ld,mid,t*2 );    buildtree( mid,rd,t*2+1 );}void incalen(int t)         {if( tree[t].ld+1 == tree[t].rd ){if( tree[t].c == 2 )tree[t].inlen = tree[t].y2 - tree[t].y1;elsetree[t].inlen = 0;}elsetree[t].inlen = tree[t<<1].inlen + tree[t<<1|1].inlen;}void updata( int t,node e ){ if( e.y2 < tree[t].y1 || e.y1 > tree[t].y2 ) return;    if( e.y1 == tree[t].y1 && e.y2 == tree[t].y2 )   //在线段树中找到边e所在的区间 更新f求出长度冷    {        tree[t].c += e.f;    }if( tree[t].ld+1 < tree[t].rd ){if( e.y2 <= tree[t<<1].y2 )   //如果e全在tree[t]的左半边updata( t<<1,e );else if( e.y1 >= tree[t<<1|1].y1 )  //e在tree[t]的右半边updata( t<<1|1,e );else if( e.y2 >= tree[t<<1|1].y1 && e.y1 <= tree[t<<1].y2 )                               //一部分在左半边 一部分在右半边{node temp = e;temp.y2 = tree[t<<1].y2;updata( t<<1,temp );temp = e;temp.y1 = tree[t<<1|1].y1;updata( t<<1|1,temp );}}    incalen(t);}int main(){//freopen("area1.in","r",stdin);//freopen("data.txt","r",stdin);    int i,j,cas,pos;    double x1,y1,x2,y2,ans;    scanf("%d",&cas);    while( cas-- )    {        scanf("%d",&n);        pos = 0;        for( i = 1; i <= n; i ++ )        {            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);            pos++;            Line[pos].x = x1;                 //存前边             Line[pos].y1 = y1;            Line[pos].y2 = y2;            Line[pos].f = 1;            y[pos] = y1;                        pos++;            Line[pos].x = x2;                  //存后边            Line[pos].y1 = y1;            Line[pos].y2 = y2;            Line[pos].f = -1;            y[pos] = y2;                    }        sort( y+1,y+pos+1);  //对横边进行排序        sort( Line+1,Line+pos+1,cmp );          //对竖边进行排序        buildtree( 1,pos,1 );        ans = 0;        for( i = 1; i <= pos; i ++ )   //当某一条线段被覆盖两次或两次以上 计算一次面积        {            ans += tree[1].inlen * ( Line[i].x - Line[i-1].x );  //tree[1].len 表示f为1的线段树长度 Line[i].x - Line[i-1].x相邻2边的距离            updata( 1,Line[i] );        }        printf("%.2lf\n",ans);    }    return 0;}