POJ1177 HDU1828 Picture，线段树求矩形并周长

/*******************************************************************************
# Author : Neo Fung
# Email : neosfung@gmail.com
# Last modified: 2012-01-25 18:57
# Filename: POJ1177 HDU1828 Picture.cpp
# Description : 线段树求矩形并
******************************************************************************/
#ifdef _MSC_VER
#define DEBUG
#endif

#include <fstream>
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <string>
#include <limits.h>
#include <algorithm>
#include <math.h>
#include <numeric>
#include <functional>
#include <ctype.h>
#define L(x) (x<<1)
#define R(x) (x<<1|1)
#define MAX 5010
using namespace std;

//length当前节点子树覆盖的长度
//num，当前节点子树中被分为多少段不连续的小段，用于计算平行于X轴的线段长度
//cover，标记当前节点是否被覆盖
//lb，rb，标记当前节点的左端点和右端点是否被覆盖，找num的数量需要用到。
struct T_NODE
{
int l,r,length,cover,num;
bool lb,rb;
}node[MAX<<2];

struct LINE
{
int x,y1,y2,flag;
}line[MAX<<1];

int y_coord[MAX<<1];

void add_line(const int &x1,const int &x2,const int &y1,const int &y2,int &cnt)
{
line[cnt].x=x1;	line[cnt].y1=y1; line[cnt].y2=y2; line[cnt].flag=1;
y_coord[cnt++]=y1;
line[cnt].x=x2;	line[cnt].y1=y1; line[cnt].y2=y2; line[cnt].flag=-1;
y_coord[cnt++]=y2;
}

bool inline cmp(const LINE &lhs,const LINE &rhs)
{
return lhs.x<rhs.x;
}

void init()
{
memset(node,0,sizeof(node));
}

void build(const int &t,const int &l,const int &r)
{
node[t].l=l;
node[t].r=r;
node[t].num = 0;
if(l==r-1)
return;
int mid=(l+r)>>1;
build(L(t),l,mid);
build(R(t),mid,r);
}

void update_len(const int &t)
{
if(node[t].cover>0)
{
node[t].num = node[t].lb =node[t].rb =1;
node[t].length = y_coord[node[t].r]-y_coord[node[t].l];
}
else if(node[t].l==node[t].r-1)
node[t].length=node[t].num=node[t].lb=node[t].rb=0;
else
{
node[t].length = node[R(t)].length+node[L(t)].length;
node[t].rb=node[R(t)].rb;
node[t].lb=node[L(t)].lb;
//如果两段的端点重合，则-1
node[t].num=node[L(t)].num+node[R(t)].num - node[L(t)].rb*node[R(t)].lb;
}

}

void update_tree(const int &t,const LINE &lne)
{
if(y_coord[node[t].l]>=lne.y1 && y_coord[node[t].r]<=lne.y2)
{
node[t].cover+=lne.flag;
update_len(t);
return;
}
if(node[t].l==node[t].r-1)
return;
int mid = (node[t].l+node[t].r)>>1;
if(lne.y1<=y_coord[mid])
update_tree(L(t),lne);
if(lne.y2>y_coord[mid])
update_tree(R(t),lne);
update_len(t);
}

__int64 solve(const int &n,const int &cnt)
{
init();
build(1,0,cnt-1);
__int64 sum=0ll;
int last =0 ,lines=0;
for(int i=0;i<n;++i)
{
update_tree(1,line[i]);
if(i>0)
sum+=2ll * lines *(line[i].x - line[i-1].x);  //求平行于X轴的边的长度
sum += abs(node[1].length - last);  //求平行于Y轴的边的长度
last = node[1].length;
lines = node[1].num;
}
return sum;
}

int main(void)
{
#ifdef DEBUG
freopen("../stdin.txt","r",stdin);
freopen("../stdout.txt","w",stdout);
#endif

int n;
int x1,y1,x2,y2;

while(~scanf("%d",&n) && n)
{
int cnt=0;
for(int i=0;i<n;++i)
{
scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
add_line(x1,x2,y1,y2,cnt);
}
sort(line,line+cnt,cmp);
sort(y_coord,y_coord+cnt);
int temp=unique(y_coord,y_coord+cnt)-y_coord;
printf("%I64d\n",solve(cnt,temp));
}

return 0;
}