【贪心】【POJ-1065&&HDOJ-1051&&AOJ-224】Wooden Sticks

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

 

/*************************************************************************************************************
题意：有n木棒，给出长度和重量，首先setup耗时+1 如果i+1根木棒的长度和重量均小于i 则不耗时 
否则重新setup time 耗时+1 求出最少的setup time
思路：首先按关键字进行排序 然后遍历找出符合条件的元素
*************************************************************************************************************/
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
typedef struct
{
    int l;
    int w;
}st;
st a[5000+10];
bool flag[5000+10];
bool cmp(st x , st y)
{
    if(x.l == y.l) return x.w < y.w;
    return x.l < y.l;
}
int main()
{
    //freopen("data.in", "r", stdin);
    //freopen("data.out", "w", stdout);
    int t;
    scanf("%d", &t);
    while(t--)
    {
        memset(flag , false , sizeof(flag));
        int n;
        scanf("%d", &n);
        for(int i = 0 ; i < n ; i++)
            scanf("%d %d", &a[i].l, &a[i].w);
        sort(a, a + n , cmp);
        int ans = 0;
        for(int i = 0 ; i < n ; i ++)
        {
            if(flag[i])
                continue;
            st temp = a[i];
            ans++;
            for(int j = i + 1; j < n ; j++)
            {
                if(a[j].l <= temp.l && a[j].w <= temp.w && !flag[j])
                {
                    flag[j] = true;
                    temp = a[j];
                }
            }
        }
        printf("%d
" , ans);
    }
    return 0;
}