HDU 1051 Wooden Sticks 贪心||DP

Posted 2020-09-27

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 22000    Accepted Submission(s): 8851

Problem Description

There is a pile of n wooden sticks. The length and weight of each stick are known in advance. The sticks are to be processed by a woodworking machine in one by one fashion. It needs some time, called setup time, for the machine to prepare processing a stick. The setup times are associated with cleaning operations and changing tools and shapes in the machine. The setup times of the woodworking machine are given as follows: 

(a) The setup time for the first wooden stick is 1 minute. 
(b) Right after processing a stick of length l and weight w , the machine will need no setup time for a stick of length l‘ and weight w‘ if l<=l‘ and w<=w‘. Otherwise, it will need 1 minute for setup. 

You are to find the minimum setup time to process a given pile of n wooden sticks. For example, if you have five sticks whose pairs of length and weight are (4,9), (5,2), (2,1), (3,5), and (1,4), then the minimum setup time should be 2 minutes since there is a sequence of pairs (1,4), (3,5), (4,9), (2,1), (5,2).

 

 

Input

The input consists of T test cases. The number of test cases (T) is given in the first line of the input file. Each test case consists of two lines: The first line has an integer n , 1<=n<=5000, that represents the number of wooden sticks in the test case, and the second line contains n 2 positive integers l1, w1, l2, w2, ..., ln, wn, each of magnitude at most 10000 , where li and wi are the length and weight of the i th wooden stick, respectively. The 2n integers are delimited by one or more spaces.

 

 

Output

The output should contain the minimum setup time in minutes, one per line.

 

 

Sample Input

3 5 4 9 5 2 2 1 3 5 1 4 3 2 2 1 1 2 2 3 1 3 2 2 3 1

 

 

Sample Output

2 1 3

 

 

Source

Asia 2001, Taejon (South Korea)

思路：将木棒按l,w 递减的顺序排列，统计关于递减的连续子列的个数即为答案。

代码：

 

 1 #include "cstdio"
 2 #include "iostream"
 3 #include "algorithm"
 4 #include "string"
 5 #include "cstring"
 6 #include "queue"
 7 #include "cmath"
 8 #include "vector"
 9 #include "map"
10 #include "stdlib.h"
11 #include "set"
12 #define mj
13 #define db double
14 #define ll long long
15 using  namespace std;
16 const int N=1e6+5;
17 const int mod=1e9+7;
18 const ll inf=1e16+10;
19 bool u[N];
20 typedef  struct stu{
21     int l,w;
22 }M;
23 M s[5005];
24 int cmp(M a,M b)
25 {
26     if(a.l==b.l) return a.w>=b.w;
27     return a.l>=b.l;
28 }
29 int main()
30 {
31     int t,n,i,j,ans;
32     scanf("%d",&t);
33     while(t--)
34     {
35         scanf("%d",&n);
36         for(i=0;i<n;i++)
37             scanf("%d%d",&s[i].l,&s[i].w),u[i]=0;
38         sort(s,s+n,cmp);
39         int mi;
40         ans=0;
41         for(i=0;i<n;i++)
42         {
43             if(u[i]) continue;
44             mi=s[i].w;
45             for(j=i+1;j<n;j++)
46             {
47                 if(!u[j]&&s[j].w<=mi){
48                     mi=s[j].w;
49                     u[j]=1;
50                 }
51             }
52             ans++;
53         }
54         printf("%d\n",ans);
55     }
56     return 0;
57 }