ZOJ Problem Set–1405 Tanning Salon

Time Limit: 2 Seconds      Memory Limit: 65536 KB

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Tan Your Hide, Inc., owns several coin-operated tanning salons. Research has shown that if a customer arrives and there are no beds available, the customer will turn around and leave, thus costing the company a sale. Your task is to write a program that tells the company how many customers left without tanning.

The input consists of data for one or more salons, followed by a line containing the number 0 that signals the end of the input. Data for each salon is a single line containing a positive integer, representing the number of tanning beds in the salon, followed by a space, followed by a sequence of uppercase letters. Letters in the sequence occur in pairs. The first occurrence indicates the arrival of a customer, the second indicates the departure of that same customer. No letter will occur in more than one pair. Customers who leave without tanning always depart before customers who are currently tanning. There are at most 20 beds per salon.

For each salon, output a sentence telling how many customers, if any, walked away. Use the exact format shown below.

Sample Input

2 ABBAJJKZKZ
3 GACCBDDBAGEE
3 GACCBGDDBAEE
1 ABCBCA
0

Sample Output

All customers tanned successfully.
1 customer(s) walked away.
All customers tanned successfully.
2 customer(s) walked away.

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Source: Mid-Central USA 2002

注意：当新的顾客来到的时候，如果没有多余的设备，用户可以等待，而不是马上就走了。

#include<iostream>
#include<string>
#include<set>
using namespace std;
int main()
{
  int salons;
  string customers;
  while(cin>>salons && salons && cin>>customers)
  {
    set<char> inUsed;
    set<char> wait;
    int walkAway = 0;
    for(int i = 0; i < customers.length(); i++)
    {
      if(inUsed.find(customers[i]) != inUsed.end())
      {
        inUsed.erase(customers[i]);
        if(wait.size() != 0)
        {
          inUsed.insert(*wait.begin());
          wait.erase(wait.begin());
        }
      }
      else if(inUsed.size() >= salons)
      {
        if(wait.find(customers[i]) != wait.end())
        {
          wait.erase(customers[i]);
          walkAway++;
        }
        else
          wait.insert(customers[i]);
      }
      else
        inUsed.insert(customers[i]);
    }
    if(walkAway != 0)
    {
      cout<<walkAway<< " customer(s) walked away."<<endl;
    }
    else
    {
      cout<<"All customers tanned successfully."<<endl;
    }
  }
  return 0;
}