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poj 1456 Supermarket

2016-01-26 14:04 232 查看

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Supermarket

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 10818		Accepted: 4742

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)=Σx∈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.

这题我用了贪心；

首先按利润进行从高到低排序；

然后一个个安排时间；

优先放在截止日；

如果已经被占，就向前挪一天，直到下限为止；

#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
#include<cstdio>
using namespace std;
struct product
{
int profit;
int deadline;
};
bool comp(const product a,const product b)
{
return a.profit>b.profit;
}
int main()
{
int n;
product p[10000];
while(scanf("%d",&n)!=EOF)
{
int sum=0;
bool flag[10000]={0};
for(int i=0;i<n;++i)
{
scanf(" %d %d",&p[i].profit,&p[i].deadline);
}
//利润从高到底排序
sort(p,p+n,comp);
for(int i=0;i<n;++i)
{
//优先放在截止日
if(flag[p[i].deadline]==0)
{
sum+=p[i].profit;
flag[p[i].deadline]=1;
}
else{
//向前挪位置
for(int j=p[i].deadline-1;j>=1;--j)
{
if(flag[j]==0)
{
sum+=p[i].profit;
flag[j]=1;
break;
}
}
}
}
printf("%d\n",sum);
}
return 0;
}

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