Wooden Sticks

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

题意是：将木棍放在机器里处理，第一根需要一分钟，剩余的如果大于等于前边放入的长度和重量，就不用费时间，否则需要一分钟，计算给出一组数的最少时间！用贪心算出最少降序序列个数！

C++版本一

贪心算法

先排序---后选择第一个没有用过的木头一次向后找，用掉所有可以用掉的木头，然后返回第一个没用过的木头继续找

#include <iostream>
#include <stdio.h>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;

int n,t;
int a[5100],b[5100];
int vis[5100];


int main()
{
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        for(int i=0;i<n;i++)
            scanf("%d%d",&a[i],&b[i]);
        memset(vis,0,sizeof(vis));
        int k;
        for(int i=0;i<n;i++){
                k=i;
            for(int j=i+1;j<n;j++){


                if(a[k]>a[j]||(a[k]==a[j]&&b[k]>b[j]))
                    k=j;
            }
            if(k!=i){
                long temp;
                temp=a[k];
                a[k]=a[i];
                a[i]=temp;

                temp=b[k];
                b[k]=b[i];
                b[i]=temp;

            }
        }
//        for(int i=0;i<n;i++)
//            printf("%d %d\n",a[i],b[i]);
        int ans=0;
        for(int i=0;i<n;i++){
            if(vis[i]==0){
                ans++;
                vis[i]=1;
                int nowl=a[i];
                int noww=b[i];
                for(int j=i+1;j<n;j++){
                    if(vis[j]==0&&nowl<=a[j]&&noww<=b[j]){
                        nowl=a[j];
                        noww=b[j];
                        vis[j]=1;
                       // cout << a[j]<<b[j] << endl;
                    }
                }
            }
        }
         cout << ans << endl;

    }

    //cout << "Hello world!" << endl;
    return 0;
}

C++版本二

DP

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
#define INF 0x3f3f3f3f
#define MAX 5000+10
struct node{
	int l,w;
}num[MAX];
bool cmp(node a,node b)
{
	if(a.l==b.l)
	return a.w<b.w;
	return a.l<b.l;
}
int dp[MAX];
int a[MAX];
int main()
{
	int t,n,i,j,sum;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%d",&n);
		for(i=1;i<=n;i++)
		{
			scanf("%d%d",&num[i].l,&num[i].w);
		}
		sort(num+1,num+1+n,cmp);
		dp[1]=0;
		sum=0;
		for(i=1;i<=n;i++)
		{
			a[i]=num[i].w;
			for(j=1;j<=sum;j++)
			if(dp[j]<=a[i])
			{
				dp[j]=a[i];
				break;
			}
			if(j>sum)
			dp[++sum]=a[i];
		}
		printf("%d\n",sum);
	}
	return 0;
}

C++版本三

#include <iostream>
#include <algorithm>
using namespace std;
#define N 5005
int num[N];
 
struct stick_node{
	int l,w;
};
stick_node stick[N];
 
bool cmpt(int a,int b){
	return a>b;
}
 
bool cmpl(stick_node a,stick_node b){
	if (a.l<b.l)
		return true;
	return false;
}
 
int main(){
#ifndef ONLINE_JUDGE
	freopen("1051in.txt","r",stdin);
#endif
	int t,n,i,j,k;
	scanf("%d",&t);
	while (t--){
		scanf("%d",&n);
		for (i=0;i<n;i++){
			scanf("%d%d",&stick[i].l,&stick[i].w);
			num[i]=0;
		}
		sort(stick,stick+n,cmpl);
		k=1;
		for (i=0;i<n;i++){
			for (j=0;j<k;j++)
				if (stick[i].w>=num[j]){
					num[j]=stick[i].w;
					break;
				}
			if (j>=k){
				num[k]=stick[i].w;
				k++;
			}
		}
		printf("%d\n",k);
	}
	return 0;
}