ACM DP Wooden Sticks

B - Wooden Sticks

Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%lld & %llu

Submit Status

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

Output for the Sample Input

2 
1 
3

 

贪心就不多说了，直接给代码了

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

struct Stick
{
    int l;
    int w;
}stick[5005];

bool cmp(const Stick a,const Stick b)
{
    if(a.l == b.l)
        return a.w < b.w;
    return a.l < b.l;
}

bool vis[5005];
int n ,t;
int main()
{
    while(~scanf("%d",&t))
    {
        while(t--)
        {
            scanf("%d",&n);
            for(int i = 0; i < n; i++)
            {
                scanf("%d%d",&stick[i].l,&stick[i].w);
            }
            sort(stick,stick + n ,cmp);

            memset(vis,0,sizeof(vis));
            int num = 0;
            int l,w;
            int cnt = 0,tt = 0;

            while(tt < n)
            {
                vis[num] = 1;
                tt++;
                l = stick[num].l;
                w = stick[num].w;
                bool flag = false;

                for(int i = num + 1; i < n;i++)
                {
                    if(!vis[i]&&stick[i].l >= l && stick[i].w >= w)
                    {
                        w = stick[i].w;
                        l = stick[i].l;
                        vis[i] = 1;
                        tt++;
                    }
                    else if(!vis[i]&&!flag)
                    {
                        flag = true;
                        num = i;
                    }
                }
                cnt++;
            }
            printf("%d
",cnt);
        }
    }
    return 0;
}