POJ 1065 Wooden Sticks(贪心,)
2018-01-21 22:35
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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 ( 9 , 4 ) , ( 2 , 5 ) , ( 1 , 2 ) , ( 5 , 3 ) , and ( 4 , 1 ) , then the minimum setup time should be
2 minutes since there is a sequence of pairs ( 4 , 1 ) , ( 5 , 3 ) , ( 9 , 4 ) , ( 1 , 2 ) , ( 2 , 5 ) .
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 2n 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
Sample Output
题目理解:
开头花费时间1,如果后面有木棒的长度l和重量w都大于等于前一根,那就不用花时间。简单来说,就是让尽量多木棒能 接在其他木棒后面,贪心题。
解题思路:
sort排序自定义以l或者w递增排序,然后按正序判断后面是否有木棒可以免费接,因为我们一开始已经以l(w)作排序,所以直接以w(l)比较,如果可以接上,更新刚接上的木棒的l(w),因为接上这根木棒,后面可能还有木棒能继续接。每一次判断前都要判断是否已经接过了(1 用标记数组标记是否用过 2 数据清0,判断数据是否为0)
重点: 1:标记判断
2:排序对比,尾部更新。
下面附上代码:
#include <iostream>
#include <cstdio>
#include <string.h>
#include <algorithm>
#include <map>
using namespace std;
struct mubang
{
int l;
int w;
}mb[5005];
int cmp(mubang a,mubang b)
{
if(a.l<b.l)
return 1;
if(a.l==b.l&&a.w<b.w)
return 1;
return 0;
}
int main()
{
int n,i,j,cas,ok[5005],ans=0,wei;
cin>>cas;
while(cas--)
{
ans=0;
memset(ok,0,sizeof(ok));
cin>>n;
for(i=0;i<n;i++)
cin>>mb[i].l>>mb[i].w;
sort(mb,mb+n,cmp);
for(i=0;i<n;i++)
{
if(ok[i]==1)
continue;
ans++;
wei=mb[i].w;
for(j=i+1;j<n;j++)
{
if(ok[j]==1)
continue;
if(mb[j].w>=wei)
{
ok[j]=1;
wei=mb[j].w;
}
}
}
cout<<ans<<endl;
}
return 0;
}
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 ( 9 , 4 ) , ( 2 , 5 ) , ( 1 , 2 ) , ( 5 , 3 ) , and ( 4 , 1 ) , then the minimum setup time should be
2 minutes since there is a sequence of pairs ( 4 , 1 ) , ( 5 , 3 ) , ( 9 , 4 ) , ( 1 , 2 ) , ( 2 , 5 ) .
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 2n 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
题目理解:
开头花费时间1,如果后面有木棒的长度l和重量w都大于等于前一根,那就不用花时间。简单来说,就是让尽量多木棒能 接在其他木棒后面,贪心题。
解题思路:
sort排序自定义以l或者w递增排序,然后按正序判断后面是否有木棒可以免费接,因为我们一开始已经以l(w)作排序,所以直接以w(l)比较,如果可以接上,更新刚接上的木棒的l(w),因为接上这根木棒,后面可能还有木棒能继续接。每一次判断前都要判断是否已经接过了(1 用标记数组标记是否用过 2 数据清0,判断数据是否为0)
重点: 1:标记判断
2:排序对比,尾部更新。
下面附上代码:
#include <iostream>
#include <cstdio>
#include <string.h>
#include <algorithm>
#include <map>
using namespace std;
struct mubang
{
int l;
int w;
}mb[5005];
int cmp(mubang a,mubang b)
{
if(a.l<b.l)
return 1;
if(a.l==b.l&&a.w<b.w)
return 1;
return 0;
}
int main()
{
int n,i,j,cas,ok[5005],ans=0,wei;
cin>>cas;
while(cas--)
{
ans=0;
memset(ok,0,sizeof(ok));
cin>>n;
for(i=0;i<n;i++)
cin>>mb[i].l>>mb[i].w;
sort(mb,mb+n,cmp);
for(i=0;i<n;i++)
{
if(ok[i]==1)
continue;
ans++;
wei=mb[i].w;
for(j=i+1;j<n;j++)
{
if(ok[j]==1)
continue;
if(mb[j].w>=wei)
{
ok[j]=1;
wei=mb[j].w;
}
}
}
cout<<ans<<endl;
}
return 0;
}
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