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 ) .
(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
先附上AC代码:
#include
#include
#include
#include
using namespace std;
pair
int cmp(pair
if(a.first==b.first) return a.second
int main(){
int T,n;
cin>>T;
int dp[5005];
while(T--){
memset(dp,0,sizeof(dp));
scanf("%d",&n);
for(int i=0;i
sort(a,a+n,cmp); //对第一属性进行排序,然后第二属性求最长递减数列,长度即为所求(与之前做过的最少拦截系统类似)
for(int i=0;i
if(dp[i]==0) dp[i]=1;
}
int maxn=0;
for(int i=0;i
printf("%d\n",maxn);
}
return 0;
}
这道题想了很久都没有思路,最后发现与最少拦截系统类似,不过就是相当于一个改编而已,而且是属于那种换汤不换药的改编。
在做ACM题时,我觉得应该多在头脑中积累一些典型的例题,毕竟即便是出题人也不可能凭空就出来一道题(这种可能非常非常小),出题人肯定也是根据现有的题进行加工改变,而如果我们积累了一些典型的例题,未必不能很快的解出答案,实现AC.