Poj 1013 Counterfeit Dollar / OpenJudge 1013(2692) 假币问题

1.链接地址：

http://poj.org/problem?id=1013

http://bailian.openjudge.cn/practice/2692

http://bailian.openjudge.cn/practice/1013

2.题目：

Counterfeit Dollar

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 37454		Accepted: 11980

Description

Sally Jones has a dozen Voyageur silver dollars. However, only eleven of the coins are true silver dollars; one coin is counterfeit even though its color and size make it indistinguishable from the real silver dollars. The counterfeit coin has a different weight from the other coins but Sally does not know if it is heavier or lighter than the real coins.
Happily, Sally has a friend who loans her a very accurate balance
scale. The friend will permit Sally three weighings to find the
counterfeit coin. For instance, if Sally weighs two coins against each
other and the scales balance then she knows these two coins are true.
Now if Sally weighs

one of the true coins against a third coin and the scales do not
balance then Sally knows the third coin is counterfeit and she can tell
whether it is light or heavy depending on whether the balance on which
it is placed goes up or down, respectively.

By choosing her weighings carefully, Sally is able to ensure that
she will find the counterfeit coin with exactly three weighings.

Input

The
first line of input is an integer n (n > 0) specifying the number of
cases to follow. Each case consists of three lines of input, one for
each weighing. Sally has identified each of the coins with the letters
A--L. Information on a weighing will be given by two strings of letters
and then one of the words ``up'', ``down'', or ``even''. The first
string of letters will represent the coins on the left balance; the
second string, the coins on the right balance. (Sally will always place
the same number of coins on the right balance as on the left balance.)
The word in the third position will tell whether the right side of the
balance goes up, down, or remains even.

Output

For
each case, the output will identify the counterfeit coin by its letter
and tell whether it is heavy or light. The solution will always be
uniquely determined.

Sample Input

1
ABCD EFGH even
ABCI EFJK up
ABIJ EFGH even 

Sample Output

K is the counterfeit coin and it is light. 

Source

East Central North America 1998

3.思路：

枚举法，枚举全部情况即可

4.代码：

 #include <iostream>
 #include <cstdio>
 #include <string>

 using namespace std;

 int main()
 {
     string str_left[];
     string str_right[];
     string str_res[];

     int n;
     cin>>n;

     int i,j,k;

     while(n--)
     {
         for(i = ; i < ; ++i) cin>>str_left[i]>>str_right[i]>>str_res[i];
         for(i = ; i < ; ++i)
         {
             for(j = ; j < ; ++j)
             {
                 for(k = ; k < ; ++k)
                 {
                     char ch = 'A' + i;
                     string::size_type idx_left = str_left[k].find(ch);
                     string::size_type idx_right = str_right[k].find(ch);

                     if(idx_left != string::npos)
                     {
                         if(j == ) //heavy
                         {
                             if(str_res[k] != "up") break;
                         }
                         else
                         {
                             if(str_res[k] != "down") break;
                         }
                     }
                     else if(idx_right != string::npos)
                     {
                         if(j == )
                         {
                             if(str_res[k] != "down") break;
                         }
                         else
                         {
                             if(str_res[k] != "up") break;
                         }
                     }
                     else
                     {
                         if(str_res[k] != "even") break;
                     }

                 }
                 if(k >= ) break;
             }
             if(j < ) break;
         }
         if(j == ) cout<<(char)('A' + i)<<" is the counterfeit coin and it is heavy."<<endl;
         else cout<<(char)('A' + i)<<" is the counterfeit coin and it is light."<<endl;
     }
     return ;
 }