poj 1177/USACO 5.5 Picture 线段树+离散化+扫描线

题意：给出n个矩形，若某条边的一段被某个矩形覆盖，则这一段就会消失，求剩下的边的总长度。

分析：仍然要用到扫描线，跟hdu 1255有点类似。因为要统计的边分为横的和竖的，所以就分两次统计。

其他的操作和hdu 1255的基本相同，只是统计的时候变了一些而已，具体的看代码。

代码：

{ID: ymwbegi1PROG: pictureLANG: PASCAL}var  n,a1,i:longint;  x1,y1,x2,y2:array[1..5000] of real;  s,ans:real;  t:array[1..10000,1..4] of longint;  a:array[0..10000] of real;  bian:array[0..10000,1..3] of real;  b:array[0..10000] of longint;procedure qsort1(l,r:longint);var  i,j:longint;  k,w:real;begin  if l>=r then exit;  i:=l;  j:=r;  k:=bian[(i+j) div 2,1];  w:=b[(l+r) div 2];  repeat    while (bian[i,1]<k)or(bian[i,1]=k)and(b[i]>w) do inc(i);    while (bian[j,1]>k)or(bian[j,1]=k)and(b[j]<w) do dec(j);    if i<=j then    begin      bian[0]:=bian[i];bian[i]:=bian[j];bian[j]:=bian[0];      b[0]:=b[i];b[i]:=b[j];b[j]:=b[0];      inc(i);dec(j);    end;  until i>j;  qsort1(i,r);  qsort1(l,j);end;procedure qsort2(l,r:longint);var  i,j:longint;  k:real;begin  if l>=r then exit;  i:=l;  j:=r;  k:=a[(i+j) div 2];  repeat    while a[i]<k do inc(i);    while a[j]>k do dec(j);    if i<=j then    begin      a[0]:=a[i];a[i]:=a[j];a[j]:=a[0];      inc(i);dec(j);    end;  until i>j;  qsort2(i,r);  qsort2(l,j);end;procedure hehe(d,l,r:longint);var  m:longint;begin  t[d,1]:=l;  t[d,2]:=r;  t[d,3]:=0;  t[d,4]:=0;  if r-l=1 then exit;  m:=(l+r) div 2;  hehe(d*2,l,m);  hehe(d*2+1,m,r);end;procedure insert(d:longint;l,r:real;z:longint);var  m:longint;begin  m:=(t[d,1]+t[d,2]) div 2;  if (a[t[d,1]]=l)and(a[t[d,2]]=r) then  begin    if t[d,4]=0      then begin             t[d,4]:=2;             t[d,3]:=t[d,3]+z;             if (t[d,3]=0)or(t[d,3]=z) then ans:=ans+r-l;           end      else if t[d,4]=1             then begin                    insert(d*2,l,a[m],z);                    insert(d*2+1,a[m],r,z);                  end             else begin                    t[d,3]:=t[d,3]+z;                    if (t[d,3]=0)or(t[d,3]=z) then ans:=ans+r-l;                  end;    exit;  end;  if t[d,4]=2 then  begin    t[d*2,4]:=2;    t[d*2+1,4]:=2;    t[d*2,3]:=t[d*2,3]+t[d,3];    t[d*2+1,3]:=t[d*2+1,3]+t[d,3];  end;  t[d,4]:=1;  if r<=a[m]    then insert(d*2,l,r,z)    else if l>=a[m]           then insert(d*2+1,l,r,z)           else begin                  insert(d*2,l,a[m],z);                  insert(d*2+1,a[m],r,z);                end;end;procedure work1;begin  for i:=1 to n do  begin    bian[i*2-1,1]:=y1[i];    bian[i*2-1,2]:=x1[i];    bian[i*2-1,3]:=x2[i];    b[i*2-1]:=1;    bian[i*2,1]:=y2[i];    bian[i*2,2]:=x1[i];    bian[i*2,3]:=x2[i];    b[i*2]:=-1;    a[i*2-1]:=x1[i];    a[i*2]:=x2[i];  end;  qsort1(1,n*2);  qsort2(1,n*2);  a1:=n*2;  for i:=1 to n*2-1 do    if a[i]=a[i+1] then    begin      a[i]:=maxlongint div 10;      dec(a1);    end;  qsort2(1,n*2);  hehe(1,1,a1);  i:=1;  bian[0,1]:=-1;  bian[n*2+1,1]:=-1;  while i<=n*2 do  begin    insert(1,bian[i,2],bian[i,3],b[i]);    while bian[i,1]=bian[i+1,1] do    begin      inc(i);      insert(1,bian[i,2],bian[i,3],b[i]);    end;    inc(i);  end;end;procedure work2;begin  for i:=1 to n do  begin    bian[i*2-1,1]:=x1[i];    bian[i*2-1,2]:=y1[i];    bian[i*2-1,3]:=y2[i];    b[i*2-1]:=1;    bian[i*2,1]:=x2[i];    bian[i*2,2]:=y1[i];    bian[i*2,3]:=y2[i];    b[i*2]:=-1;    a[i*2-1]:=y1[i];    a[i*2]:=y2[i];  end;  qsort1(1,n*2);  qsort2(1,n*2);  a1:=n*2;  for i:=1 to n*2-1 do    if a[i]=a[i+1] then    begin      a[i]:=maxlongint div 10;      dec(a1);    end;  qsort2(1,n*2);  hehe(1,1,a1);  i:=1;  bian[0,1]:=-1;  bian[n*2+1,1]:=-1;  while i<=n*2 do  begin    insert(1,bian[i,2],bian[i,3],b[i]);    while bian[i,1]=bian[i+1,1] do    begin      inc(i);      insert(1,bian[i,2],bian[i,3],b[i]);    end;    inc(i);  end;end;begin  assign(input,'picture.in');  assign(output,'picture.out');  reset(input);  rewrite(output);  readln(n);  for i:=1 to n do    readln(x1[i],y1[i],x2[i],y2[i]);  ans:=0;  work1;  work2;  writeln(ans:0:0);  close(input);  close(output);end.