【HDOJ6638】Snowy Smile（线段树）

题意：一个二维平面上有n个点，每个点的坐标是（x[i]，y[i]），权值是w[i]

求一个矩形使得其中所有点的权值和最大，输出权值和

n<=2e3，x[i]，y[i]，w[i]的绝对值<=1e9

思路：

  1 #include<bits/stdc++.h>
  2 using namespace std;
  3 typedef long long ll;
  4 typedef unsigned int uint;
  5 typedef unsigned long long ull;
  6 typedef pair<int,int> PII;
  7 typedef pair<ll,ll> Pll;
  8 typedef vector<int> VI;
  9 typedef vector<PII> VII;
 10 #define N  110000
 11 #define M  4100000
 12 #define fi first
 13 #define se second
 14 #define MP make_pair
 15 #define pi acos(-1)
 16 #define mem(a,b) memset(a,b,sizeof(a))
 17 #define rep(i,a,b) for(int i=(int)a;i<=(int)b;i++)
 18 #define per(i,a,b) for(int i=(int)a;i>=(int)b;i--)
 19 #define lowbit(x) x&(-x)
 20 #define Rand (rand()*(1<<16)+rand())
 21 #define id(x) ((x)<=B?(x):m-n/(x)+1)
 22 #define ls p<<1
 23 #define rs p<<1|1
 24 
 25 const ll MOD=998244353,inv2=(MOD+1)/2;
 26       double eps=1e-6;
 27       int INF=1e9;
 28 
 29 ll t1[N<<2],t2[N<<2],t3[N<<2],t4[N<<1];
 30 int x[N],y[N],w[N],X[N],Y[N];
 31 VII V[N];
 32 
 33 int read()
 34 {
 35    int v=0,f=1;
 36    char c=getchar();
 37    while(c<48||57<c) {if(c=='-') f=-1; c=getchar();}
 38    while(48<=c&&c<=57) v=(v<<3)+v+v+c-48,c=getchar();
 39    return v*f;
 40 }
 41 
 42 void clear(int l,int r,int p)
 43 {
 44     t1[p]=t2[p]=t3[p]=t4[p]=0;
 45     if(l==r) return;
 46     int mid=(l+r)>>1;
 47     clear(l,mid,ls);
 48     clear(mid+1,r,rs);
 49 }
 50 
 51 void pushup(int p)
 52 {
 53     t1[p]=t1[ls]+t1[rs];
 54     t2[p]=max(t2[ls],t1[ls]+t2[rs]);
 55     t3[p]=max(t3[rs],t1[rs]+t3[ls]);
 56     t4[p]=max(max(t4[ls],t4[rs]),t3[ls]+t2[rs]);
 57 }
 58 
 59 void update(int l,int r,int x,int v,int p)
 60 {
 61     if(l==r)
 62     {
 63         t1[p]+=v;
 64         t2[p]=t3[p]=t4[p]=max(t1[p],0ll);
 65         return;
 66     }
 67     int mid=(l+r)>>1;
 68     if(x<=mid) update(l,mid,x,v,ls);
 69      else update(mid+1,r,x,v,rs);
 70     pushup(p);
 71 }
 72 
 73 int main()
 74 {
 75     //freopen("1.in","r",stdin);
 76     int cas=read();
 77     while(cas--)
 78     {
 79         int n=read();
 80         X[0]=Y[0]=0;
 81         rep(i,1,n)
 82         {
 83             x[i]=read(),y[i]=read(),w[i]=read();
 84             X[++X[0]]=x[i];
 85             Y[++Y[0]]=y[i];
 86         }
 87         sort(X+1,X+X[0]+1);
 88         sort(Y+1,Y+Y[0]+1);
 89         X[0]=unique(X+1,X+X[0]+1)-X-1;
 90         Y[0]=unique(Y+1,Y+Y[0]+1)-Y-1;
 91         rep(i,1,n)
 92         {
 93             x[i]=lower_bound(X+1,X+X[0]+1,x[i])-X;
 94             y[i]=lower_bound(Y+1,Y+Y[0]+1,y[i])-Y;
 95         }
 96         rep(i,1,X[0]) VII().swap(V[i]);
 97         rep(i,1,n) V[x[i]].push_back(MP(y[i],w[i]));
 98         //printf("isok\n");
 99         ll ans=0;
100         rep(i,1,X[0])
101         {
102             clear(1,Y[0],1);
103             rep(j,i,X[0])
104             {
105                 for(int k=0;k<V[j].size();k++) update(1,Y[0],V[j][k].fi,V[j][k].se,1);
106                 ans=max(ans,t4[1]);
107             }
108         }
109         printf("%I64d\n",ans);
110     }
111 
112     return 0;
113 }