http://acm.hdu.edu.cn/showproblem.php?pid=1051
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
题意分析:
有n个木棍,已知它们的长度和重量,现在要把它们一一加工,每个木棍有一个设置时间。
设置时间与清洁操作和更改机器中的工具和形状有关,设置时间的规定:
a.第一个加工的木棍的设置时间为1;
b.在加工了长度为 l 重量为 w 的木棍之后,如果下一个加工的木棍的长度和重量都不小于前一个,就不需要设置时间,
否则需要1分钟的设置时间。
求把所有木棍加工完需要的最小的设置时间。
解题思路:
按照长度排个序,如果长度相同,按照重量排序。
如果后面一个木棍的长度和重量有一个小于前面的,另外考虑,
首先挑出长度最短的一个,从后面找出最近的一个符合条件的,找到最后还有剩余就重复前面的过程,直到所有的木棍都被加工完成。
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define N 5050
struct data{
int w;
int l;
}a[N], t;
int book[N];
int cmp(data a, data b)
{
if(a.l!=b.l)
return a.l<b.l;
return a.w<b.w;
}
int main()
{
int T, n, i, j, ans;
scanf("%d" ,&T);
while(T--)
{
scanf("%d", &n);
for(i=0; i<n; i++)
scanf("%d%d", &a[i].l, &a[i].w);
sort(a, a+n, cmp);
memset(book, 0, sizeof(book));
j=0;
ans = 0;
while(j<n)
{
for(i=0; i<n; i++)
if(book[i]==0)
{
t=a[i];
book[i] = 1;
j++;
ans++;
break;
}
i++;
for(; i<n; i++)
{
if(a[i].l>=t.l && a[i].w>=t.w && book[i]==0)
{
j++;
book[i] = 1;
t=a[i];
}
}
}
printf("%d
", ans);
}
return 0;
}