【POJ 2482】 Stars in Your Windows

【题目链接】

            http://poj.org/problem?id=2482

【算法】

            线段树 + 扫描线

【代码】

           

#include <algorithm>  
#include <bitset>  
#include <cctype>  
#include <cerrno>  
#include <clocale>  
#include <cmath>  
#include <complex>  
#include <cstdio>  
#include <cstdlib>  
#include <cstring>  
#include <ctime>  
#include <deque>  
#include <exception>  
#include <fstream>  
#include <functional>  
#include <limits>  
#include <list>  
#include <map>  
#include <iomanip>  
#include <ios>  
#include <iosfwd>  
#include <iostream>  
#include <istream>  
#include <ostream>  
#include <queue>  
#include <set>  
#include <sstream>  
#include <stdexcept>  
#include <streambuf>  
#include <string>  
#include <utility>  
#include <vector>  
#include <cwchar>  
#include <cwctype>  
#include <stack>  
#include <limits.h> 
using namespace std;
#define MAXN 10010
typedef long long ll;

struct info
{
        ll x,l,r,v;
} a[MAXN<<1];

ll i,n,w,h,len,lth,ans,l,r;
ll x[MAXN],y[MAXN],c[MAXN],val[MAXN<<1];

struct SegmentTree
{
        struct Node
        {
                ll l,r;
                ll mx,tag;
        } Tree[MAXN<<4];
        inline void build(ll index,ll l,ll r)
        {
                ll mid;
                Tree[index].l = l; Tree[index].r = r;
                Tree[index].mx = 0;
                if (l == r) return;
                mid = (Tree[index].l + Tree[index].r) >> 1;
                build(index<<1,l,mid);
                build(index<<1|1,mid+1,r); 
        }
        inline void update(ll index)
        {
                Tree[index].mx = max(Tree[index<<1].mx,Tree[index<<1|1].mx);
        }
        inline void pushdown(ll index)
        {
                 if (Tree[index].tag)
                 {
                         Tree[index<<1].mx += Tree[index].tag;
                        Tree[index<<1|1].mx += Tree[index].tag;
                        Tree[index<<1].tag += Tree[index].tag;
                        Tree[index<<1|1].tag += Tree[index].tag;
                        Tree[index].tag = 0;        
                }
        }
        inline void add(ll index,ll l,ll r,ll val)
        {
                ll mid;
                if (l > r) return;
                if (Tree[index].l == l && Tree[index].r == r)
                {
                        Tree[index].mx += val;
                        Tree[index].tag += val; 
                } else
                {
                        pushdown(index);
                        mid = (Tree[index].l + Tree[index].r) >> 1;
                        if (mid >= r) add(index<<1,l,r,val);
                        else if (mid + 1 <= l) add(index<<1|1,l,r,val);
                        else
                        {
                                add(index<<1,l,mid,val);
                                add(index<<1|1,mid+1,r,val);
                        }
                        update(index);
                }
        }
        inline ll get()
        {
                return Tree[1].mx;
        }
} T;
inline bool cmp(info a,info b)
{
        return (a.x != b.x) ? (a.x < b.x) : (a.v < b.v);
}

int main() 
{
        
        while (scanf("%lld%lld%lld",&n,&w,&h) != EOF)
        {
                    len = lth = ans = 0;
                    for (i = 1; i <= n; i++)
                    {
                            scanf("%lld%lld%lld",&x[i],&y[i],&c[i]);
                            a[++len] =     (info){x[i],y[i],y[i]+h,c[i]};
                            a[++len] =  (info){x[i]+w,y[i],y[i]+h,-c[i]};
                            val[++lth] = y[i];
                            val[++lth] = y[i] + h;
                    }    
                    sort(val+1,val+lth+1);
                    lth = unique(val+1,val+lth+1) - val - 1; 
                    sort(a+1,a+len+1,cmp); 
                    T.build(1,1,lth);
                    for (i = 1; i <= len; i++)
                    {
                            l = lower_bound(val+1,val+lth+1,a[i].l) - val;
                            r = lower_bound(val+1,val+lth+1,a[i].r) - val - 1;
                            T.add(1,l,r,a[i].v);
                            ans = max(ans,T.get());
                    }                    
                    printf("%lld\n",ans);
        } 
        
        return 0;      
    
}