HDU5091 Beam Cannon(线段树扫描线)

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#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
const int maxn=40005;
const int bw=20000;

#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)

int lc[maxn<<2],rc[maxn<<2],ad[maxn<<2],nd[maxn<<2];
inline void pushup(int u){

    nd[u]=max(nd[lson(u)],+nd[rson(u)])+ad[u];
}
inline void maintain(int u,int v){
    ad[u]+=v;
    nd[u]+=v;
}
void build(int u,int l,int r){
    lc[u]=l;
    rc[u]=r;
    ad[u]=nd[u]=0;
    if(l==r) return ;
    int mid=(l+r)>>1;
    build(lson(u),l,mid);
    build(rson(u),mid+1,r);
    pushup(u);
}
void modify(int u,int l,int r,int v){
    if(l<=lc[u]&&rc[u]<=r){
        maintain(u,v);
        return ;
    }
    int mid=(lc[u]+rc[u])>>1;
    if(l<=mid) modify(lson(u),l,r,v);
    if(r>mid) modify(rson(u),l,r,v);
    pushup(u);
}
int query(int u,int l,int r){
    if(l<=lc[u]&&rc[u]<=r)
        return nd[u];
    int mid=(lc[u]+rc[u])>>1 ,ret=0;
    if(l<=mid) ret=max(ret,query(lson(u),l,r));
    if(r>mid) ret=max(ret,query(rson(u),l,r));
    pushup(u);
    return ret;
}
struct Seg{
    int x,l,r,w;
    Seg(int x=0,int l=0,int r=0,int w=0){
        this->x=x;
        this->l=l;
        this->r=r;
        this->w=w;
    }
};
vector<Seg> G;
inline bool cmp(const Seg& a,const Seg& b){
    if(a.x != b.x) return a.x<b.x;
    return a.w<b.w;
}
int N,W,H;
void init()
{
    int x,y;
    G.clear();
    scanf("%d%d",&W,&H);
    for(int i=0;i<N;i++){
        scanf("%d%d",&x,&y);
        G.push_back(Seg(x,y+bw,min(bw,y+H)+bw,1));
        G.push_back(Seg(x+W+1,y+bw,min(bw,y+H)+bw,-1));
    }
    build(1,0,bw*2);
    sort(G.begin(),G.end(),cmp);
}
int main()
{
    while(scanf("%d",&N)==1&&N!=-1){
        init();
        int ans=0;
        for(int i=0;i<G.size();i++){
            modify(1,G[i].l,G[i].r,G[i].w);
            ans=max(ans,nd[1]);

        }
        printf("%d\n",ans);
    }
    return 0;
}

HDU5091 Beam Cannon(线段树扫描线)

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原文地址：http://blog.csdn.net/a197p/article/details/45482569