ACM 2034.

People love A-B

Time Limit: 2000/1000 MS (Java/others) memory limit: 65536/32768 K (Java/others) total submission (s): 43070 accepted submission (s): 12081

The person who participated in the Problem description last month's competition must remember one of the simplest questions: {A} + {B}. The question is the union of the two sets, today, our A-B calculates the difference between the two sets, that is, the subtraction operation of the Set. (Of course, we all know the definition of a set, that is, there will not be two identical elements in the same set. Here, I would like to remind you)
It's easy, right?

 

Each input group occupies one row. Each row starts with two integers, n (0 <= n <= 100) and M (0 <= m <= 100 ), indicates the number of elements of set a and Set B respectively, followed by N + M elements. The first n elements belong to set a, and the rest belong to Set B. each element is an integer not greater than the int value range. Each element is separated by a space. if n = 0 and m = 0, the input ends without processing.

 

Output outputs a line of data for each group of data, indicating the results of the A-B, if the results are empty set, the output "null", otherwise the output results from small to large, to simplify the problem, each element is followed by a space (PIT ).

 

Sample input3 3 1 2 3 1 4 73 7 2 5 8 2 3 4 5 6 7 8 0

 

Sample output2 3 Null

 

Authorlcy

 1 #include <map> 2 #include <iostream> 3  4 using namespace std; 5  6  7 int main() 8 { 9 10     map<int,bool> setMapA;11     int n,m,num;12     while(cin >> n >> m)13     {14         if(m == 0 && n == 0)15         {16             break;17         }18         setMapA.clear();19         for(int i = 0; i< n;i++)20         {21             cin >> num;22             setMapA.insert(pair<int,bool>(num,true));23         }24 25         for(int i = 0; i< m;i++)26         {27             cin >> num;28             setMapA[num] = false;29         }30 31         for(map<int,bool>::iterator cmp = setMapA.begin(); cmp != setMapA.end();)32         {33             if(!(cmp->second))34             {35                 setMapA.erase(cmp++);36             }else37             {38                 ++cmp;39             }40         }41 42         if(setMapA.size() == 0)43         {44             cout<<"NULL\n";45         }else46         {47             int i = 0;48             for(map<int,bool>::iterator cmp = setMapA.begin(); cmp != setMapA.end();cmp++)49             {50                 if(i != (int)setMapA.size() -1)51                 {52                     cout << cmp->first << " ";53                 }else54                 {55                     cout << cmp->first << " \n";56                 }57                 i++;58             }59 60         }61 62 63     }64 }

View code

When using the erase function in map, pay attention to setmapa. Erase (CMP ++); in this way, the information of the nodes indicated by CMP is deleted first, and then the CMP node is directed forward;
If setmapa. Erase (++ CMP); deletes the information of the next node, the link is broken, causing a bug