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 }