杭电ACM1800解题报告

Flying to the Mars

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 17306    Accepted Submission(s): 5564

Problem Description

In the year 8888, the Earth is ruled by the PPF Empire . As the population growing , PPF needs to find more land for the newborns . Finally , PPF decides to attack Kscinow who ruling the Mars . Here the problem comes! How can the soldiers reach the Mars ? PPF convokes his soldiers and asks for their suggestions . “Rush … ” one soldier answers. “Shut up ! Do I have to remind you that there isn’t any road to the Mars from here!” PPF replies. “Fly !” another answers. PPF smiles :“Clever guy ! Although we haven’t got wings , I can buy some magic broomsticks from HARRY POTTER to help you .” Now , it’s time to learn to fly on a broomstick ! we assume that one soldier has one level number indicating his degree. The soldier who has a higher level could teach the lower , that is to say the former’s level > the latter’s . But the lower can’t teach the higher. One soldier can have only one teacher at most , certainly , having no teacher is also legal. Similarly one soldier can have only one student at most while having no student is also possible. Teacher can teach his student on the same broomstick .Certainly , all the soldier must have practiced on the broomstick before they fly to the Mars! Magic broomstick is expensive !So , can you help PPF to calculate the minimum number of the broomstick needed .
For example :
There are 5 soldiers (A B C D E)with level numbers : 2 4 5 6 4;
One method :
C could teach B; B could teach A; So , A B C are eligible to study on the same broomstick.
D could teach E;So D E are eligible to study on the same broomstick;
Using this method , we need 2 broomsticks.
Another method:
D could teach A; So A D are eligible to study on the same broomstick.
C could teach B; So B C are eligible to study on the same broomstick.
E with no teacher or student are eligible to study on one broomstick.
Using the method ,we need 3 broomsticks.
……

After checking up all possible method, we found that 2 is the minimum number of broomsticks needed.

 

Input

Input file contains multiple test cases.
In a test case,the first line contains a single positive number N indicating the number of soldiers.(0<=N<=3000)
Next N lines :There is only one nonnegative integer on each line , indicating the level number for each soldier.( less than 30 digits);

 

Output

For each case, output the minimum number of broomsticks on a single line.

 

Sample Input

4 10 20 30 04 5 2 3 4 3 4

 

Sample Output

1 2

 

英语这么长头都看晕了吧？其实题意很简单，每个士兵都有等级（数字代表），高级可当低级的老师，一个士兵只能有一个或零个老师，也只能有一个或零个学生，能串起来的老师学生们就共用一个扫把，计算至少要多少个扫把。

注意点：

士兵的等级是一个不超过30位的数字，很大，做起来容易超时；

解题思路：

其实就是计算所有重复数字的最大次数，因为数组很大，所有我没有使用这种方法，担心超时，但是你们也可以试一试用。我用的方法是，先从小到大排序，用双重循环，从第一个开始，逐个检索到最后一个满足连成串的要求，被连的数字不再检索。

附c++代码：

#include using namespace std; int main(){  int n,i,j,c,k,a[3002];;  while(scanf("%d",&n)!=EOF){   k=0;   for(i=0;i