View Compilation Error

0_0_37338723_6966.cpp: In function 'void prepare()':
0_0_37338723_6966.cpp:36:37: error: invalid types 'std::map<std::basic_string<char>, int>::mapped_type {aka int}[std::map<std::basic_string<char>, int>::mapped_type {aka int}]' for array subscript
    edge[s[x]][s[y]] = edge[s[y][s[x]] = time;
                                     ^
0_0_37338723_6966.cpp:36:45: error: expected ']' before ';' token
    edge[s[x]][s[y]] = edge[s[y][s[x]] = time;
                                             ^