POJ 2482 Stars in Your Window 线段树扫描线
Description
These days, having parted with friends, roommates and classmates one after another, I still cannot believe the fact that after waving hands, these familiar faces will soon vanish from our life and become no more than a memory. I will move out from school tomorrow. And you are planning to fly far far away, to pursue your future and fulfill your dreams. Perhaps we will not meet each other any more if without fate and luck. So tonight, I was wandering around your dormitory building hoping to meet you there by chance. But contradictorily, your appearance must quicken my heartbeat and my clumsy tongue might be not able to belch out a word. I cannot remember how many times I have passed your dormitory building both in Zhuhai and Guangzhou, and each time aspired to see you appear in the balcony or your silhouette that cast on the window. I cannot remember how many times this idea comes to my mind: call her out to have dinner or at least a conversation. But each time, thinking of your excellence and my commonness, the predominance of timidity over courage drove me leave silently.
Graduation, means the end of life in university, the end of these glorious, romantic years. Your lovely smile which is my original incentive to work hard and this unrequited love will be both sealed as a memory in the deep of my heart and my mind. Graduation, also means a start of new life, a footprint on the way to bright prospect. I truly hope you will be happy everyday abroad and everything goes well. Meanwhile, I will try to get out from puerility and become more sophisticated. To pursue my own love and happiness here in reality will be my ideal I never desert.
Farewell, my princess!
If someday, somewhere, we have a chance to gather, even as gray-haired man and woman, at that time, I hope we can be good friends to share this memory proudly to relight the youthful and joyful emotions. If this chance never comes, I wish I were the stars in the sky and twinkling in your window, to bless you far away, as friends, to accompany you every night, sharing the sweet dreams or going through the nightmares together.
Here comes the problem: Assume the sky is a flat plane. All the stars lie on it with a location (x, y). for each star, there is a grade ranging from 1 to 100, representing its brightness, where 100 is the brightest and 1 is the weakest. The window is a rectangle whose edges are parallel to the x-axis or y-axis. Your task is to tell where I should put the window in order to maximize the sum of the brightness of the stars within the window. Note, the stars which are right on the edge of the window does not count. The window can be translated but rotation is not allowed.
Input
There are at least 1 and at most 10000 stars in the sky. 1<=W,H<=1000000, 0<=x,y<2^31.
Output
Sample Input
3 5 4
1 2 3
2 3 2
6 3 1
3 5 4
1 2 3
2 3 2
5 3 1
Sample Output
5
6
题意:
给你一个w*h的矩形,和平面上n个点,每个点有权值
问你用这个矩形能框住最大的点权和,要球必须在这个矩形内部
题解:
将点的范围延展成矩形,用扫描线去扫
线段树维护区间最值
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<map>
#include<vector>
using namespace std;
const int N = 2e6+, M = 1e6+, mod = 1e9+, inf = 2e9+;
typedef long long ll; int n,w,h;
ll y[N];
struct Line{
ll top,x,down,f;
Line() {}
Line ( ll a,ll b,ll c,ll d ) { top=a,x=b,down=c,f=d;}
}line[N];
bool cmp(Line s1,Line s2) {
if(s1.x==s2.x) return s1.f<s2.f;
else return s1.x<s2.x;
}
map<ll ,int > H;
ll mx[N*],l[N*],r[N*],lazy[N*];
void pushdown(int k) {
if(lazy[k]==) return ;
ll tmp = lazy[k];
lazy[k] = ;
mx[k<<]+=tmp;
mx[k<<|]+=tmp;
lazy[k<<] += tmp;
lazy[k<<|] += tmp;
}
void build(int k,int s,int t) {
l[k] = s;
r[k] = t;
mx[k] = ;
lazy[k] = ;
if(s==t) return ;
int mid = (s+t)>>;
build(k<<,s,mid);
build(k<<|,mid+,t);
}
void update(int k,int x,int y,ll c) {
pushdown(k);
if(l[k]==x&&r[k]==y) {
mx[k] += c;
lazy[k] += c;
return ;
} int mid = (l[k]+r[k])>>;
if(y<=mid) update(k<<,x,y,c);
else if(x>mid) update(k<<|,x,y,c);
else update(k<<,x,mid,c),update(k<<|,mid+,y,c); mx[k] = max(mx[k<<],mx[k<<|]);
}
int main() {
while(scanf("%d%d%d",&n,&w,&h)!=EOF) {
int cnt = ;
H.clear(); for(int i=;i<=n;i++) {
ll a,b,c;
scanf("%I64d%I64d%I64d",&a,&b,&c);
line[++cnt] = Line(b+h-,a,b,c);
y[cnt] = b;
line[++cnt] = Line(b+h-,a+w,b,-c);
y[cnt] = b+h-;
} sort(y+,y+cnt+);
sort(line+,line++cnt,cmp);
int c = unique(y+,y+cnt+) - y - ;
for(int i=;i<=c;i++) H[y[i]] = i; build(,,c);
ll ans = ;
for(int i=;i<=cnt;i++) {
update(,H[line[i].down],H[line[i].top],line[i].f);
ans = max(ans,mx[]);
}
printf("%I64d\n",ans);
}
return ;
}
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