POJ 2482 Stars in Your Window(线段树+扫描线)

题目链接

非常不容易的一道题，把每个点向右上构造一个矩形，将问题转化为重合矩形那个亮度最大，注意LL，注意排序。

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <string>

  4 #include <algorithm>

  5 using namespace std;

  6 #define maxn 50100

  7 #define lson l,m,rt<<1

  8 #define rson m+1,r,rt<<1|1

  9 #define LL __int64

 10 struct node

 11 {

 12     LL lx,rx,y;

 13     LL s;

 14     node(){}

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

 16     bool operator < (const node &S) const

 17     {

 18         if(y == S.y)

 19         return s > S.s;

 20         else

 21         return y < S.y;

 22     }

 23 }mat[maxn];

 24 LL que[2*maxn];

 25 LL tree[4*maxn];

 26 LL lz[4*maxn];

 27 void pushup(int rt)

 28 {

 29     tree[rt] = max(tree[rt<<1],tree[rt<<1|1]);

 30 }

 31 void pushdown(int rt)

 32 {

 33     if(lz[rt])

 34     {

 35         lz[rt<<1] += lz[rt];

 36         lz[rt<<1|1] += lz[rt];

 37         tree[rt<<1] += lz[rt];

 38         tree[rt<<1|1] += lz[rt];

 39         lz[rt] = 0;

 40     }

 41 }

 42 void update(int L,int R,int c,int l,int r,int rt)

 43 {

 44     int m;

 45     if(L <= l&&r <= R)

 46     {

 47         tree[rt] += c;

 48         lz[rt] += c;

 49         return ;

 50     }

 51     pushdown(rt);

 52     m = (l+r)>>1;

 53     if(L <= m)

 54     update(L,R,c,lson);

 55     if(R > m)

 56     update(L,R,c,rson);

 57     pushup(rt);

 58 }

 59 int bin(LL x,int n)

 60 {

 61     int str,mid,end;

 62     str = 0;

 63     end = n;

 64     while(str <= end)

 65     {

 66         mid = (str+end)/2;

 67         if(que[mid] == x)

 68         return mid;

 69         else if(que[mid] > x)

 70         end = mid - 1;

 71         else

 72         str = mid + 1;

 73     }

 74     return mid;

 75 }

 76 int main()

 77 {

 78     int n,num,k,i;

 79     LL a,b,c,h,w;

 80     while(scanf("%d%I64d%I64d",&n,&w,&h)!=EOF)

 81     {

 82         num = 0;

 83         w--;

 84         h--;

 85         for(i = 0;i < n;i ++)

 86         {

 87             scanf("%I64d%I64d%I64d",&a,&b,&c);

 88             mat[num] = node(a,a+w,b,c);

 89             que[num++] = a;

 90             mat[num] = node(a,a+w,b+h,-c);

 91             que[num++] = a+w;

 92         }

 93         k = 1;

 94         sort(que,que+num);

 95         sort(mat,mat+num);

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

 97         {

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

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

100         }

101         LL maxz = 0;

102         memset(tree,0,sizeof(tree));

103         memset(lz,0,sizeof(lz));

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

105         {

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

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

108             if(l <= r) update(l,r,mat[i].s,0,k-1,1);

109             maxz = max(maxz,tree[1]);

110         }

111         printf("%I64d\n",maxz);

112     }

113     return 0;

114 }