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2013
12-23

HDU 1800 Flying to the Mars[解题报告] C++

Flying to the Mars

问题描述 :


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.

输入:

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);

输出:

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

样例输入:

4
10
20
30
04
5
2
3
4
3
4

样例输出:

1
2

题意:有N个士兵,每个士兵有一个属于自己的等级,他们要学一项魔杖飞行技术,等级高的士兵可以教等级低的士兵,等级低的士兵不可以教等级高的士兵,一个士兵只能教一个士兵,一个士兵也只能被一个士兵教,能形成这样的教学关系的士兵组成一个教学组,需要一根魔杖,问最少需要多少根魔杖。

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1800

——>>一个严格递增的序列需要一根魔杖,那么有多少个严格递增的序列就需要多少根魔杖,也就是哪个数字重复次数最多,该数字重复的次数就是所需的魔杖数。

开始用数组统计次数,RE,接着,用multiset来统计,TLE,最后,用map过了。

map<int, int> ma;第一个int代表士兵的等级,第二个int代表这个等级的士兵的人数,输入所有士兵的等级后,遍历一次map,取第二个int的最大值就是答案。

#include <cstdio>
#include <map>
#include <algorithm>

using namespace std;

map<int, int> ma;

int main()
{
    int N, p, i;
    while(scanf("%d", &N) == 1)
    {
        if(!N) continue;
        ma.clear();
        for(i = 1; i <= N; i++)
        {
            scanf("%d", &p);
            if(ma.find(p) == ma.end())
            {
                ma[p] = 1;
            }
            else
            {
                ma[p]++;
            }
        }
        int maxx = -1;
        for(map<int, int>::const_iterator t = ma.begin(); t != ma.end(); t++)
        {
            int cnt = t->second;
            maxx = max(maxx, cnt);
        }
        printf("%d\n", maxx);
    }
    return 0;
}

解题报告转自:http://blog.csdn.net/scnu_jiechao/article/details/9380033