【杭电oj1051】Wooden Sticks

                               Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 18623    Accepted Submission(s): 7614

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)

 

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We have carefully selected several similar problems for you:   1050  1045  1053  1789  1003 

 

先对长度进行排序，因为长度大小顺序确定了，所以只需要比较重量，把某个重量递增的序列标记，记录总够查找的次数，就是所求。

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 5005;
struct node {
	int len,wei;
} s[N];
bool vis[N];
bool cmp(node A,node B) {
	if(A.len==B.len)
		return A.wei<B.wei;
	return A.len<B.len;
}
int main() {
	int T,n;
	scanf("%d",&T);
	while(T--) {
		scanf("%d",&n);
		for(int i=0; i<n; i++) {
			scanf("%d%d",&s[i].len,&s[i].wei);
		}
		sort(s,s+n,cmp);
		int ans=0,cnt,flag;
		memset(vis,false,sizeof(vis));
		for(int i=0; i<n; i++) {
			if(vis[i])
				continue;
			else {
				vis[i]=true;
				cnt=s[i].wei;
				for(int j=i+1; j<n; j++) {
					if(s[j].wei>=cnt&&!vis[j]) {	//for条件没写全，wa了一次。 
						cnt=s[j].wei;		//此处j写成了i哇了一次，基本功不够扎实啊 
						vis[j]=true;
					}
				}
			}
			ans++;
		}
		printf("%d\n",ans);
	}
	return 0;
}

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1051