description

analysis

其实可以贪心
先把区间按左端点排序，转折点也排序
扫一次转折点，把所有左端点在当前点左边的区间丢进优先队列里
按照贪心策略，对于某个转折点，一定选择右端点离它最近的区间
于是把不合法（右端点在转折点左边）的区间弹出，匹配下去就好了

code

#pragma GCC optimize("O3")

#pragma G++ optimize("O3")

#include<stdio.h>

#include<string.h>

#include<algorithm>

#include<queue>

#define MAXN 200005

#define ll long long

#define reg register ll

#define fo(i,a,b) for (reg i=a;i<=b;++i)

#define fd(i,a,b) for (reg i=a;i>=b;--i)

using namespace std;

priority_queue <ll,vector<ll>,greater<ll> > q;

ll n,m,now=1,ans;

ll b[MAXN];

struct node

{

	ll x,y;

}a[MAXN];

inline ll read()

{

	ll x=0,f=1;char ch=getchar();

	while (ch<'0' || '9'<ch){if (ch=='-')f=-1;ch=getchar();}

	while ('0'<=ch && ch<='9')x=x*10+ch-'0',ch=getchar();

	return x*f;

}

inline bool cmp(node a,node b){return a.x<b.x;}

int main()

{

	freopen("T2.in","r",stdin);

	//freopen("dream.in","r",stdin);

	//freopen("dream.out","w",stdout);

	n=read(),m=read();

	fo(i,1,n)a[i].x=read(),a[i].y=read();

	fo(i,1,m)b[i]=read();

	sort(a+1,a+n+1,cmp),sort(b+1,b+m+1);

	fo(i,1,m)

	{

		while (a[now].x<=b[i] && now<=n)q.push(a[now++].y);

		while (!q.empty() && b[i]>q.top())q.pop();

		if (!q.empty() && b[i]<=q.top())++ans,q.pop();

	}

	printf("%lld\n",ans);

	return 0;

}

巴特西

【JZOJ6274】梦境

description

analysis

code

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