Hdu oj 1800 Flying to the Mars(Map）

Flying to the Mars

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 16035    Accepted Submission(s): 5148

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

410203004523434

 

Sample Output

12

 

Author

PPF@JLU

真是要死在这道题上了，花式超时，这道题说白了就是问哪个数出现次数最多，输出这个次数。好吧，噩梦开始。这道题直接做肯定是不行的，因为这个数最长的有30位，所以我第一直觉是map和哈希（看题解还有字典树，然而我不会）。题里说可能有前导0，所以我把字符数组A里的非0字符转移到字符数组B里，稳稳TLE。然后我又用迭代器直接删0，也是TLE。最后我把更新Max单独拿出来用迭代器更新，这才对QAQ，要注意00000代表0，所以只迭代到str.end()-1；

#include<iostream>#include<cstdio>#include<cmath>#include<map>#include<string>using namespace std;int Max(int x,int y){    return x>y?x:y;}int main(){    int n;    while(~scanf("%d",&n))    {        int j;        map<string,int >M;        string a;        for(j=0;j<n;j++)        {            cin>>a;            for(string::iterator its = a.begin();*its == '0'&&its<a.end()-1;a.erase(its));            M[a]++;        }        int count = 0;for(map<string, int>::iterator it = M.begin(); it != M.end(); it++ ){count = Max( count, it->second );}        printf("%d\n",count);    }}