3044 矩形面积求并 - Wikioi

题目描述 Description

输入n个矩形，求他们总共占地面积（也就是求一下面积的并）

输入描述 Input Description

可能有多组数据，读到n=0为止(不超过15组)

每组数据第一行一个数n，表示矩形个数(n<=100)

接下来n行每行4个实数x1,y1,x2,y1(0 <= x1 < x2 <= 100000;0 <= y1 < y2 <= 100000)，表示矩形的左下角坐标和右上角坐标

输出描述 Output Description

每组数据输出一行表示答案

样例输入 Sample Input

2
    10 10 20 20
    15 15 25 25.5
    0

样例输出 Sample Output

180.00

水题，我只是拿来练习扫描线的

 const
         maxn=;
 type
         node=record
           l,r,lc,rc,cnt:longint;
           sum,cover:double;
         end;
 var
         tree:array[..maxn*]of node;
         x:array[..maxn*]of double;
         l,r,c:array[..maxn*]of longint;
         y,lll,rrr:array[..maxn*]of double;
         n,tot,ll,rr:longint;
         ans:double;

 procedure swap(var x,y:longint);
 var
         t:longint;
 begin
         t:=x;x:=y;y:=t;
 end;

 procedure swap(var x,y:double);
 var
         t:double;
 begin
         t:=x;x:=y;y:=t;
 end;

 procedure sort(l,r:longint);
 var
         i,j:longint;
         y:double;
 begin
         i:=l;
         j:=r;
         y:=x[(l+r)>>];
         repeat
           while x[i]<y do
             inc(i);
           while x[j]>y do
             dec(j);
           if i<=j then
           begin
             swap(x[i],x[j]);
             inc(i);
             dec(j);
           end;
         until i>j;
         if i<r then sort(i,r);
         if j>l then sort(l,j);
 end;

 procedure build(l,r:longint);
 var
         now,mid:longint;
 begin
         inc(tot);
         now:=tot;
         tree[now].l:=l;
         tree[now].r:=r;
         with tree[now] do
           begin
             cover:=;
             cnt:=;
             if l=r then
             begin
               sum:=x[r+]-x[r];
               lc:=;
               rc:=;
               exit;
             end;
             mid:=(l+r)>>;
             lc:=tot+;
             build(l,mid);
             rc:=tot+;
             build(mid+,r);
             sum:=x[r+]-x[l];
           end;
 end;

 procedure sort2(ll,rr:longint);
 var
         i,j:longint;
         z:double;
 begin
         i:=ll;
         j:=rr;
         z:=y[(ll+rr)>>];
         repeat
           while y[i]<z do
             inc(i);
           while y[j]>z do
             dec(j);
           if i<=j then
           begin
             swap(l[i],l[j]);
             swap(r[i],r[j]);
             swap(y[i],y[j]);
             swap(c[i],c[j]);
             inc(i);
             dec(j);
           end;
         until i>j;
         if i<rr then sort2(i,rr);
         if j>ll then sort2(ll,j);
 end;

 function find(k:double):longint;
 var
         l,r,mid:longint;
 begin
         l:=;
         r:=n*;
         while l<>r do
           begin
             mid:=(l+r)>>;
             if x[mid]=k then exit(mid);
             if x[mid]>k then r:=mid-
             else l:=mid+;
           end;
         exit(l);
 end;

 procedure init;
 var
         i:longint;
         x1,y1,x2,y2:double;
 begin
         read(n);
         if n= then halt;
         ans:=;
         tot:=;
         for i:= to n do
           begin
             read(x1,y1,x2,y2);
             lll[i*-]:=x1;
             rrr[i*-]:=x2;
             y[i*-]:=y1;
             c[i*-]:=;
             lll[i*]:=x1;
             rrr[i*]:=x2;
             y[i*]:=y2;
             c[i*]:=-;
             x[i*-]:=x1;
             x[i*]:=x2;
           end;
         sort(,n*);
         build(,n*-);
         for i:= to n* do
           begin
             l[i]:=find(lll[i]);
             r[i]:=find(rrr[i]);
           end;
         sort2(,n*);
 end;

 procedure insert(now,c:longint);
 var
         mid:longint;
 begin
         with tree[now] do
           begin
             if (ll<=l) and (rr>=r) then
             begin
               inc(cnt,c);
               if cnt> then cover:=sum
               else cover:=tree[lc].cover+tree[rc].cover;
               exit;
             end;
             mid:=(l+r)>>;
             if ll<=mid then insert(lc,c);
             if rr>mid then insert(rc,c);
             if cnt> then cover:=sum
             else cover:=tree[lc].cover+tree[rc].cover;
           end;
 end;

 procedure work;
 var
         i:longint;
 begin
         for i:= to n* do
           begin
             if y[i]<>y[i-] then ans:=ans+tree[].cover*(y[i]-y[i-]);
             ll:=l[i];
             rr:=r[i]-;
             insert(,c[i]);
           end;
         writeln(ans::);
 end;

 begin
         while true do
           begin
             init;
             work;
           end;
 end.