Stall Reservations Page43 贪心+优先队列
题意:给出N个区间,将其不重叠地放在数轴上,至少需要几个数轴? [1, 2],[2, 3]算作重叠
贪心思想:将区间左端点从小到大排序,在遍历的同时,用优先队列记录下当前所有数轴的最小右端点,如果该区间能放进其中一个数轴,就放进去,并修改最右端点,如果放不进去,那么就新建一个数轴
代码:
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<set>
#include<list>
#include<deque>
#include<queue>
#include<map>
#define ll long long
#define pb push_back
#define rep(x,a,b) for (int x=a;x<=b;x++)
#define repp(x,a,b) for (int x=a;x<b;x++)
#define W(x) printf("%d\n",x)
#define WW(x) printf("%lld\n",x)
#define pi 3.14159265358979323846
#define mem(a,x) memset(a,x,sizeof a)
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
using namespace std;
const int maxn=2e6+7;
const int INF=1e9;
const ll INFF=1e18;
int ans[maxn],m=0,n;
struct node
{
int l,r,id;
bool operator<(const node &x)const
{
return r>x.r;
}
}p[maxn];
bool cmp(node a,node b)
{
if (a.l==b.l)return a.r<b.r;
else return a.l<b.l;
}
priority_queue<node> Q;
int main()
{
scanf("%d",&n);
rep(i,1,n)
{
scanf("%d%d",&p[i].l,&p[i].r);
p[i].id=i;
}
sort(p+1,p+1+n,cmp);
rep(i,1,n)
{
if (Q.empty())
{
Q.push(p[i]);
ans[p[i].id]=++m;
continue;
}
node u=Q.top();
if (p[i].l>u.r)
{
Q.pop();
Q.push(p[i]);
ans[p[i].id]=ans[u.id];
}
else
{
Q.push(p[i]);
ans[p[i].id]=++m;
}
}
W(m);rep(i,1,n)W(ans[i]);
return 0;
}