poj2482Stars in Your Window(线段树+离散化+扫描线）

http://poj.org/problem?id=2482

类似于上一篇 这题转化的比较巧妙 将一个点转化为一个矩形(x,y, x+w,y+h),扫描线入值为正 出值为负

也就是一根线过去 每进入一个矩形 都更新线上的总值 取一个最大值

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 using namespace std;
 #define N 20010
 #define LL long long
 struct node
 {
     LL lx,rx,y,s;
     node(){}
     node(LL a,LL b,LL c,LL d):lx(a),rx(b),y(c),s(d){}
     bool operator <(const node &S)const
     {
         if(y==S.y)
         return s>S.s;
         return y<S.y;
     }
 }te[N];
 int sum[N<<],cov[N<<],que[N];
 int bin(LL x,int n)
 {
     int s=,e = n,m;
     while(s<=e)
     {
         m = (s+e)/;
         if(que[m]==x)
         return m;
         else if(que[m]>x)
         e = m-;
         else
         s = m+;
     }
     return m;
 }
 void pushdown(int w)
 {
     if(cov[w])
     {
         cov[w<<] += cov[w];
         cov[w<<|] += cov[w];
         sum[w<<] += cov[w];
         sum[w<<|] += cov[w];
         cov[w] = ;
     }
 }
 void pushup(int w)
 {
     sum[w] = max(sum[w<<],sum[w<<|]);
 }
 void update(int a,int b,int d,int l,int r,int w)
 {
     if(a<=l&&b>=r)
     {
         sum[w]+=d;
         cov[w]+=d;
         return ;
     }
     pushdown(w);
     int m = (l+r)>>;
     if(a<=m)
     update(a,b,d,l,m,w<<);
     if(b>m)
     update(a,b,d,m+,r,w<<|);
     pushup(w);
 }
 int main()
 {
     int i,k,n;
     LL w,h,x,y,v;
     while(cin>>n>>w>>h)
     {
         int num = ;
         w--;h--;
         for(i = ; i <= n ;i++)
         {
             cin>>x>>y>>v;
             que[num] = x;
             te[num++] = node(x,x+w,y,v);
             que[num] = x+w;
             te[num++] = node(x,x+w,y+h,-v);
         }
         sort(que,que+num);
         sort(te,te+num);
         k = ;
         for(i =  ; i < num ; i++)
         {
             if(que[i]!=que[i-])
             que[k++] = que[i];
         }
         int maxz = ;
         for(i =  ; i < num ; i++)
         {
             int l = bin(te[i].lx,k-);
             int r = bin(te[i].rx,k-);
             update(l,r,te[i].s,,k-,);
             maxz = max(maxz,sum[]);
         }
         cout<<maxz<<endl;
     }
     return ;
 }