HDU 1082 Matrix Chain Multiplication

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <map>
 5 #include <string>
 6 
 7 using namespace std;
 8 
 9 struct matrix{
10     int row,col;
11 };
12 
13 int main(){
14     int n;
15     cin >>n;
16     map<string,matrix> a;
17     for(int i = 0;i < n; i ++ ){
18         string name;
19         int r,c;
20         cin>>name>>r>>c;
21         matrix tmpm;
22         tmpm.row = r;
23         tmpm.col = c;
24         a.insert(pair<string,matrix>(name,tmpm));
25     }
26     vector<string> ebnf;
27     string tmp;
28     while(cin >>tmp) ebnf.push_back(tmp);
29 
30     for(int i = 0; i < ebnf.size(); i ++ ){
31         vector<string> sstack;
32         int cnt = 0;
33         bool error = false;
34         for(int j = 0; j < ebnf[i].length(); j ++ ){
35             if(ebnf[i][j] == '(') continue;
36             else if(ebnf[i][j] != ')') {
37                 string tmp = "";
38                 tmp +=ebnf[i][j];
39                 sstack.push_back( tmp);
40             }
41             else{
42                 int idx = sstack.size()-1;
43                 if( a[sstack[idx-1]].col != a[sstack[idx]].row ) { error = true; break;}
44                 cnt += a[sstack[idx-1]].row*a[sstack[idx-1]].col*a[sstack[idx]].col;
45                 string newName = sstack[idx-1]+sstack[idx];
46                 int newRow = a[sstack[idx-1]].row, newCol = a[sstack[idx]].col;
47 
48                 matrix tmpm;
49                 tmpm.row = newRow;
50                 tmpm.col = newCol;
51 
52                 a.insert( pair<string,matrix>( newName,tmpm) );
53                 sstack.pop_back();sstack.pop_back();
54                 sstack.push_back(newName);
55             }
56         }
57         if(error) cout<<"error"<<endl;
58         else cout<<cnt<<endl;
59         sstack.clear();
60     }
61     return 0;
62 }

第一次在codeforces上能编译通过，但提交时报

error C2678: 二进制“>>”: 没有找到接受“std::istream”类型的左操作数的运算符(或没有可接受的转换)

结果是因为没有加#include <string>

当再次用codeforces编译时仍能通过，但提交时报错

a.insert(pair<string,matrix>(name,{t,c}));//不能通过

利用了个临时变量将其改为

        matrix tmpm;
        tmpm.row = r;
        tmpm.col = c;
        a.insert(pair<string,matrix>(name,tmpm));