Stall Reservations
Time Limit: 1000MS | Memory Limit: 65536K | |||
Total Submissions: 10068 | Accepted: 3555 | Special Judge |
Description
Oh those picky N (1 <= N <= 50,000) cows! They are so picky that each one will only be milked over some precise time interval A..B (1 <= A <= B <= 1,000,000), which includes both times A and B. Obviously, FJ must create a reservation system to determine which stall each cow can be assigned for her milking time. Of course, no cow will share such a private moment with other cows.
Help FJ by determining:
Help FJ by determining:
- The minimum number of stalls required in the barn so that each cow can have her private milking period
- An assignment of cows to these stalls over time
Input
Line 1: A single integer, N
Lines 2..N+1: Line i+1 describes cow i's milking interval with two space-separated integers.
Lines 2..N+1: Line i+1 describes cow i's milking interval with two space-separated integers.
Output
Line 1: The minimum number of stalls the barn must have.
Lines 2..N+1: Line i+1 describes the stall to which cow i will be assigned for her milking period.
Lines 2..N+1: Line i+1 describes the stall to which cow i will be assigned for her milking period.
Sample Input
5 1 10 2 4 3 6 5 8 4 7
Sample Output
4 1 2 3 2 4
Hint
Explanation of the sample:
Here's a graphical schedule for this output:
Here's a graphical schedule for this output:
Time 1 2 3 4 5 6 7 8 9 10 Stall 1 c1>>>>>>>>>>>>>>>>>>>>>>>>>>> Stall 2 .. c2>>>>>> c4>>>>>>>>> .. .. Stall 3 .. .. c3>>>>>>>>> .. .. .. .. Stall 4 .. .. .. c5>>>>>>>>> .. .. ..Other outputs using the same number of stalls are possible.
Source
考点:优先队列+贪心算法
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
int per[50010];
struct node
{
int start,end,pos;
}cow[50010],now;
bool operator < (const node &a,const node &b)//产奶结束越早的越优先
{
if(a.end==b.end)
return a.start>b.start;
return a.end>b.end;
}
int cmp(node a,node b)
{
if(a.start==b.start)
return a.end<b.end;
return a.start<b.start;
}
int main()
{
int n,i,k,cnt;
while(scanf("%d",&n)!=EOF)
{
for(i=0;i<n;++i){
scanf("%d%d",&cow[i].start,&cow[i].end);
cow[i].pos=i;
}
sort(cow,cow+n,cmp);
memset(per,0,sizeof(per));
priority_queue<node>q;
q.push(cow[0]);
per[cow[0].pos]=1;
k=1;
for(i=1;i<n;++i)
{
now=q.top();
if(cow[i].start>now.end)//同用一个挤奶机器
{
per[cow[i].pos]=per[now.pos];
q.pop(); //优先删除最早产奶结束
}
else//增加一个挤奶机器
per[cow[i].pos]=++k;
q.push(cow[i]); //入队时产奶结束最早的优先往前排队
}
printf("%d\n",k);
for(i=0;i<n;++i)
printf("%d\n",per[i]);
}
return 0;
}