Supermarket

Time Limit: 2000MS	Memory Limit: 65536K
Total Submissions: 9103	Accepted: 3891

Description

A supermarket has a set Prod of products on sale. It earns a profit px for each product x∈Prod sold by a deadline dx that is measured as an integral number of time units starting from the moment the sale begins. Each product takes precisely one unit of time for being sold. A selling schedule is an ordered subset of products Sell ≤ Prod such that the selling of each product x∈Sell, according to the ordering of Sell, completes before the deadline dx or just when dx expires. The profit of the selling schedule is Profit(Sell)=Σ_x∈Sellpx. An optimal selling schedule is a schedule with a maximum profit. 
For example, consider the products Prod={a,b,c,d} with (pa,da)=(50,2), (pb,db)=(10,1), (pc,dc)=(20,2), and (pd,dd)=(30,1). The possible selling schedules are listed in table 1. For instance, the schedule Sell={d,a} shows that the selling of product d starts at time 0 and ends at time 1, while the selling of product a starts at time 1 and ends at time 2. Each of these products is sold by its deadline. Sell is the optimal schedule and its profit is 80. 

Write a program that reads sets of products from an input text file and computes the profit of an optimal selling schedule for each set of products. 

Input

A set of products starts with an integer 0 <= n <= 10000, which is the number of products in the set, and continues with n pairs pi di of integers, 1 <= pi <= 10000 and 1 <= di <= 10000, that designate the profit and the selling deadline of the i-th product. White spaces can occur freely in input. Input data terminate with an end of file and are guaranteed correct.

Output

For each set of products, the program prints on the standard output the profit of an optimal selling schedule for the set. Each result is printed from the beginning of a separate line.

Sample Input

4  50 2  10 1   20 2   30 1

7  20 1   2 1   10 3  100 2   8 2
   5 20  50 10

Sample Output

80
185

Hint

The sample input contains two product sets. The first set encodes the products from table 1. The second set is for 7 products. The profit of an optimal schedule for these products is 185.

Source

題意： 超市裡有n個產品要賣，每個產品都有一個截至時間dx（從開始賣時算起），只有在這個截至時間之前才能賣出並且獲得率潤dy。 有多個產品，所有可以有不同的賣出順序，每賣一個產品要佔用1個單位的時間，問最多能賣出多少利潤。 解題：把產品按最後期限從大到小排，然後從最大的那個期限時間往前一天一天推，如果當前天的期限產品沒有完全賣出，就放到前一天期限，和前一天最後期限的產品一走賣，利潤大的就先賣。沒有賣出的又放到前一天去賣，這樣從大期限往小期限推，因為小期限的產品不可能在大期限時間去賣，而大期限的產品可以在小的期限去賣。

#include<stdio.h>
#include<iostream>
#include<queue>
#include<algorithm>
using namespace std;
#define N 10005
typedef struct nnn
{
    int p,d;
}node;
typedef struct nn
{
    int p;
    friend bool operator<(struct nn a,struct nn b)//優先佇列值從大到小取
    {
        return a.p<b.p;
    }
}INT;
node ans[N];
int cmp(node a,node b)//最後期限從大到小排
{
    return a.d>b.d;
}
int solve(int n,int l)
{
    int maxp=0,tl,d,i,maxd;
    priority_queue<INT>q;
    INT pp;
    i=0;
    for(maxd=ans[0].d; maxd>0;maxd--)
    {
        for( ;i<n&&maxd<=ans[i].d; i++)
        {
            pp.p=ans[i].p; q.push(pp);
        }
        tl=0;
        while(!q.empty()&&tl<l)
        {
            pp=q.top(); q.pop();
            maxp+=pp.p; tl++;
        }
    }
    return maxp;
}
int main()
{
    int n,l,i;

    while(scanf("%d",&n)>0)
    {
        for( i=0;i<n;i++)
            scanf("%d%d",&ans[i].p,&ans[i].d);
        if(n==0)
        {
            printf("0\n"); continue;
        }
        sort(ans,ans+n,cmp);
        printf("%d\n",solve(n,1));
    }
}