hdu 3697 Selecting courses (暴力+贪心)

Selecting courses

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 62768/32768 K (Java/Others)
Total Submission(s): 1856    Accepted Submission(s): 469

Problem Description

    A new Semester is coming and students are troubling for selecting courses. Students select their course on the web course system. There are n courses, the ith course is available during the time interval (A _i,B _i). That means, if you want to select the ith course, you must select it after time Ai and before time Bi. Ai and Bi are all in minutes. A student can only try to select a course every 5 minutes, but he can start trying at any time, and try as many times as he wants. For example, if you start trying to select courses at 5 minutes 21 seconds, then you can make other tries at 10 minutes 21 seconds, 15 minutes 21 seconds,20 minutes 21 seconds… and so on. A student can’t select more than one course at the same time. It may happen that no course is available when a student is making a try to select a course 

You are to find the maximum number of courses that a student can select.

 

Input

There are no more than 100 test cases.

The first line of each test case contains an integer N. N is the number of courses (0
Then N lines follows. Each line contains two integers Ai and Bi (0<=A _ii<=1000), meaning that the ith course is available during the time interval (Ai,Bi).

The input ends by N = 0.

 

Output

For each test case output a line containing an integer indicating the maximum number of courses that a student can select.

 

Sample Input

2 1 10 4 5 0

 

Sample Output

2

 

题意是：每次选一个起始点，以后只能在+5这些点上进行选课。因为数据范围比较小，可以暴力。

枚举0、1、2、3、  4这5个起点，对于每个确定的起点可以得到一些可以进行选课的点，把选课时间段以终点进行从小到大排序，枚举可得最优解。另外，区间（a,b）可以变为[a,b)，因为对于a分钟来说，a分01秒是可以选的。

#include
#include
#include
#include
#include
using namespace std;
#define N 1005
const int inf=0x3fffffff;
int mark[N];
struct node
{
    int l,r;
}g[305];
bool cmp(node a,node b)
{
    return a.r