Stall Reservations

题目链接http://poj.org/problem?id=3190

Stall Reservations

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions:10223		Accepted:3608		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:

• 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

Many answers are correct for each test dataset; a program will grade your answer.

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.

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.

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: 

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.

需要用到贪心思想的模拟题。难点是维护每一个畜栏的结束时间。

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
#include<queue>
#define DEBUG(x) cout<<#x<<" = "<<x<<endl
using namespace std;
const int MAXN=5e4+100;
struct cow{
    int s,e;
    int idx;
    cow(){}
    cow(int ss,int ee,int i):s(ss),e(ee),idx(i){}
    bool operator<(const cow &c)const
    {
        return s<c.s;
    }
};
struct stall{
    int et;
    int no;
    stall(int e,int n):et(e),no(n){}
    stall(){}
    bool operator<(const stall &s)const
    {
        return et>s.et;
    }
};
int N;
int pos[MAXN];
cow cowarray[MAXN];
int main()
{
//    freopen("in.txt","r",stdin);
    cin>>N;
    for(int i=0;i<N ;i++ ){
        int s,e;
        scanf("%d%d",&s,&e);
        cowarray[i].s=s,
        cowarray[i].e=e,
        cowarray[i].idx=i;
    }
    sort(cowarray,cowarray+N);
    priority_queue<stall>pq;
    int cnt=1;
    cow &c=cowarray[0];
    pq.push(stall(c.e,cnt));
    ///这是一个经常出现的bug，且难以发现，排序之后的下标和之前的下标不同
//    pos[0]=cnt;
    pos[c.idx]=cnt;
    for(int i=1;i<N ;i++ ){
        stall st=pq.top();
        if(st.et<cowarray[i].s){
            pq.pop();
            st.et=cowarray[i].e;
            int idx=cowarray[i].idx;
            pos[idx]=st.no;
            pq.push(st);
        }
        else{
            cnt++;
            cow &t=cowarray[i];
            pq.push(stall(t.e,cnt));
            pos[t.idx]=cnt;
        }
    }
    printf("%d
",cnt);
    for(int i=0;i<N ;i++ ){
        printf("%d
",pos[i]);
//        cout<<pos[i]<<endl;
    }
}