HDU 1051 Wooden Sticks (简单贪心)

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 8280 Accepted Submission(s): 3371


[align=left]Problem Description[/align]
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).

[align=left]Input[/align]
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.

[align=left]Output[/align]
The output should contain the minimum setup time in minutes, one per line.

[align=left]Sample Input[/align]

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

[align=left]Sample Output[/align]

2
1
3

简单的贪心题目，和导弹防御系统很类似的一道题。只需要按length从小到大排序，然后寻找递增序列的个数即可。

View Code

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
const int MN=5050;
struct wooden
{
int length;
int weight;
}node[MN],pack[MN/10];
bool cmp(struct wooden a,struct wooden b)
{
if(a.length!=b.length) return a.length<b.length;
else return a.weight<b.weight;
}
int main()
{
int cas,n,i,j;
scanf("%d",&cas);
while(cas--){
scanf("%d",&n);
for(i=0;i<n;i++){
scanf("%d%d",&node[i].length,&node[i].weight);
}
sort(node,node+n,cmp);
int b=node[0].weight;
int flag=0,o=0;
for(i=1;i<n;i++){
if(node[i].weight>=b){
b=node[i].weight;
}
else {
for(j=0;j<o;j++){
if(node[i].weight>=pack[j].weight){
pack[j].weight=node[i].weight;
break;
}
}
if(j==o) {
pack[o++].weight=node[i].weight;
}
}
}
if(i==n) flag=1;
printf("%d\n",o+flag);
}
return 0;
}