Wooden Sticks Hdu 1051 贪心算法



Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 18533    Accepted Submission(s): 7552

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

213

 

处理木块前需要对机器进行设置，如果后面放入的木块 l 和 w 都不大于前面的木块 就不用重新设置 否则重新设置，每设置一次需要花费一分钟

所以我选择先对木块进行非递增排序（l不等时 按l  l相等时 按 w）

AC

#include<stdio.h>
#include<algorithm>
using namespace std;
struct SIZE{
 int l;
 int w;
}sticks[5005];
int flag[5005];
bool cmp(const SIZE &a,const SIZE &b)
{
 if(a.l!=b.l)             //判断l是否相等 ；
 return a.l>b.l;
 else
 return a.w>b.w;
}
int main()
{
 int n,min,cases;
 int i,j,s;
 scanf("%d",&cases);
 while(cases--)
 {
  scanf("%d",&n);
  for(i=0;i<n;i++)
  {
   scanf("%d%d",&sticks[i].l,&sticks[i].w);
   flag[i]=0;
  }
  sort(sticks,sticks+n,cmp);     //按长度由大到小排序  
  s=0;
  for(i=0;i<n;i++)
  {
   min=sticks[i].w;
   if(flag[i]) continue;
   for(j=i+1;j<n;j++)       //直到[j].w>[i].w
   {
    if(min>=sticks[j].w && !flag[j])
    {
     min=sticks[j].w;
     flag[j]=1;
    }
   }
   s++;       //重新整理机器 
  }
  printf("%d\n",s);
 }
 return 0;
}