POJ 1177: Picture

#include<cstdio>
#include<iostream>
#include<sstream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<climits>
#include<cmath>
#include<algorithm>
#include<queue>
#include<vector>
#include<stack>
#include<set>
#include<map>
#define INF 0x3f3f3f3f
#define eps 1e-8
using namespace std;
const int MAXN=30000;
const int U=11000;
int cot[MAXN<<2],tr1[MAXN<<2],tr2[MAXN<<2];
bool lbd[MAXN<<2],rbd[MAXN<<2];
vector<pair<pair<int,int>,pair<int,int> > > seg;

void pushup(int rt, int l, int r)
{
if(cot[rt])
{
lbd[rt]=rbd[rt]=true;
tr1[rt]=r-l+1;
tr2[rt]=2;
}
else if(l==r)
{
lbd[rt]=rbd[rt]=false;
tr1[rt]=tr2[rt]=0;
}
else
{
lbd[rt]=lbd[rt<<1];
rbd[rt]=rbd[rt<<1|1];
tr1[rt]=tr1[rt<<1]+tr1[rt<<1|1];
tr2[rt]=tr2[rt<<1]+tr2[rt<<1|1];
if(rbd[rt<<1]&&lbd[rt<<1|1])
{
tr2[rt]-=2;
}
}
}

void update(int L, int R, int c, int l, int r, int rt)
{
if(L<=l&&r<=R)
{
cot[rt]+=c;
pushup(rt,l,r);
return;
}
int mid=(l+r)>>1;
if(L<=mid)
{
update(L,R,c,l,mid,rt<<1);
}
if(R>mid)
{
update(L,R,c,mid+1,r,rt<<1|1);
}
pushup(rt,l,r);
}

int main()
{
int n;
while(scanf("%d",&n)==1)
{
memset(cot,0,sizeof(cot));
memset(tr1,0,sizeof(tr1));
memset(tr2,0,sizeof(tr2));
memset(lbd,0,sizeof(lbd));
memset(rbd,0,sizeof(rbd));
seg.clear();
int maxi=0;
for(int i=0; i<n; i++)
{
int x1,y1,x2,y2;
scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
seg.push_back(make_pair(make_pair(y1,1),make_pair(x1+U,x2+U)));
seg.push_back(make_pair(make_pair(y2,-1),make_pair(x1+U,x2+U)));
maxi=max(maxi,x2+U);
}
sort(seg.begin(),seg.end());
int ans=0,pre=0;
for(int i=0; i<2*n; i++)
{
if(seg[i].second.first<seg[i].second.second)
{
update(seg[i].second.first,seg[i].second.second-1,seg[i].first.second,0,maxi-1,1);
}
ans+=abs(tr1[1]-pre);
pre=tr1[1];
if(i<2*n-1)
{
ans+=tr2[1]*(seg[i+1].first.first-seg[i].first.first);
}
}
printf("%d\n",ans);
}
return 0;
}