HDU ACM 1800 Flying to the Mars

原题描述

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

解题思路

题意：PPF军队要乘坐扫帚攻上火星，现在要进行训练。
每个军人都有一个等级，等级高的可以教等级低的人乘坐(与其使用同一把扫帚)
每个人最多只能有一个学生和一个老师，允许没有学生或者老师。
输入人数和等级，输出最少需要的扫帚。

此题只要求等级重复数量最多的人数即是答案。

参考代码

#include 
#include 
using namespace std;

int main()
{
    int n, i, count, max, a[3002];
    while(~scanf("%d",&n))         // 括号内 = scanf("%d",&n,n!=EOF)
    {
        for (i = 0; i < n;i++)
            scanf("%d", &a[i]);     // 使用scanf 比cin更省时间
        sort(a, a + n);             // 按等级从小到大排序
        max = 1;
        count = 1;
        for (i = 1; i < n; i++)     // 计算重复次数最多的等级
            if (a[i]>a[i - 1])
                count = 1;
            else
            {
                count++;
                max = max > count ? max : count;
            }
        printf("%d\n", max);
    }
}