sdnu-并查集-weeklyexam ——I

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.

时间有限，却想要最大收益（每个活动占用的时长还相等）

贪心想一下我们是不是只要降序排序收益，然后对于大的收益我们都要，要了之后更新老大

然后因为每一个产品都需要一个单位时间来进行，所以只要利润高及时是截至时间相同也得干，只不过就i是会的失去一些利润低的值

一旦发现T = 0 那就是项目排满了

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;

const int maxn=10010;

struct Node
{
int begin;
int end;
}node[maxn];
bool cmp(Node a,Node b)
{
return a.begin>b.begin;
}
int pre[maxn],val[maxn];
int find(int x)
{
return x == pre[x] ? x : find(pre[x]);
}
int main()
{
int n,a,b,dis,ans;
while(scanf("%d",&n) != EOF)
{
for(int i=0;i<=maxn;i++)
{
pre[i]=i;
}
ans=0;
for(int i=0;i<n;i++)
{
scanf("%d%d",&node[i].begin,&node[i].end);
}
sort(node,node+n,cmp);
for(int i=0;i < n;i++)
{
int t = find(node[i].end);
if(t>0)
{
ans+=node[i].begin;
pre[t]=t-1; //表示这一时段已经占用 //只要利润高的可以占用利润低的

}
}
cout<<ans<<endl;
}
return 0;
}