HDU 1051(贪心)

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

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 13534    Accepted Submission(s): 5590

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

 

 

题目大意：一堆木棍，有长度和重量，处理第一根需要一分钟，然后处理下一根木棍，如果这根木棍的长度和重量都不大于之前的木棍，则不需要花费时间，否则也需要一分钟。

分析：首先排序，先按长度排序，如果长度一样，则按重量排序（从小到大和从大到小排序都可以，我是按从小到大排序的）。然后求递增（减）序列的最小个数。

 

#include <cstdio>
#include <cmath>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

int T,n;
int a[5005],b[5005],vis[5001];

int main ()
{
    int i,j;
    int time;
    int x,y;
    scanf ("%d",&T);
    while (T--)
    {
        scanf ("%d",&n);
        for (i=0; i<n; i++)
            scanf ("%d %d",&a[i], &b[i]);
        for (i=0; i<n; i++)//两个for循环排序，没用结构体，比较麻烦
        {
            for (j=i; j<n; j++)
            {
                if (a[i] > a[j])
                {
                    swap(a[i], a[j]);
                    swap(b[i], b[j]);
                }
                if (a[i] == a[j])
                {
                    if (b[i] > b[j])
                    {
                        swap(a[i], a[j]);
                        swap(b[i], b[j]);
                    }
                }

            }
        }
        time = 0;
        memset(vis, 0, sizeof(vis));
        for (i=0; i<n; i++)
        {
            if (vis[i])//若该木棍被访问过，跳过
                continue;
            //x = a[i];
            y = b[i];
            for (j=i+1; j<n; j++)
            {
                if (!vis[j] && b[j] >= y)
                {

                    vis[j] = 1;//标记访问
                    //x = a[j];
                    y = b[j];//当前最大重量
                }
            }
            time++;//时间加一
        }
        printf ("%d
",time);
    }
    return 0;
}