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

  1 #include <iostream>

  2 #include<cstdio>

  3 #include<cstring>

  4 #include<algorithm>

  5 #include<stdlib.h>

  6 using namespace std;

  7 #define N 20010

  8 #define LL long long

  9 struct node

 10 {

 11     LL lx,rx,y,s;

 12     node(){}

 13     node(LL a,LL b,LL c,LL d):lx(a),rx(b),y(c),s(d){}

 14     bool operator <(const node &S)const

 15     {

 16         if(y==S.y)

 17         return s>S.s;

 18         return y<S.y;

 19     }

 20 }te[N];

 21 int sum[N<<2],cov[N<<2],que[N];

 22 int bin(LL x,int n)

 23 {

 24     int s=0,e = n,m;

 25     while(s<=e)

 26     {

 27         m = (s+e)/2;

 28         if(que[m]==x)

 29         return m;

 30         else if(que[m]>x)

 31         e = m-1;

 32         else

 33         s = m+1;

 34     }

 35     return m;

 36 }

 37 void pushdown(int w)

 38 {

 39     if(cov[w])

 40     {

 41         cov[w<<1] += cov[w];

 42         cov[w<<1|1] += cov[w];

 43         sum[w<<1] += cov[w];

 44         sum[w<<1|1] += cov[w];

 45         cov[w] = 0;

 46     }

 47 }

 48 void pushup(int w)

 49 {

 50     sum[w] = max(sum[w<<1],sum[w<<1|1]);

 51 }

 52 void update(int a,int b,int d,int l,int r,int w)

 53 {

 54     if(a<=l&&b>=r)

 55     {

 56         sum[w]+=d;

 57         cov[w]+=d;

 58         return ;

 59     }

 60     pushdown(w);

 61     int m = (l+r)>>1;

 62     if(a<=m)

 63     update(a,b,d,l,m,w<<1);

 64     if(b>m)

 65     update(a,b,d,m+1,r,w<<1|1);

 66     pushup(w);

 67 }

 68 int main()

 69 {

 70     int i,k,n;

 71     LL w,h,x,y,v;

 72     while(cin>>n>>w>>h)

 73     {

 74         int num = 0;

 75         w--;h--;

 76         for(i = 1; i <= n ;i++)

 77         {

 78             cin>>x>>y>>v;

 79             que[num] = x;

 80             te[num++] = node(x,x+w,y,v);

 81             que[num] = x+w;

 82             te[num++] = node(x,x+w,y+h,-v);

 83         }

 84         sort(que,que+num);

 85         sort(te,te+num);

 86         k = 1;

 87         for(i = 1 ; i < num ; i++)

 88         {

 89             if(que[i]!=que[i-1])

 90             que[k++] = que[i];

 91         }

 92         int maxz = 0;

 93         for(i = 0 ; i < num ; i++)

 94         {

 95             int l = bin(te[i].lx,k-1);

 96             int r = bin(te[i].rx,k-1);

 97             update(l,r,te[i].s,0,k-1,1);

 98             maxz = max(maxz,sum[1]);

 99         }

100         cout<<maxz<<endl;

101     }

102     return 0;

103 }

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