View Compilation Error

0_0_30154868_27710.cpp:2:2: error: expected unqualified-id before 'while'
  while( ! q.empty()) {   v = q.front();   q.pop_front();   for( i = 1;i <= m;i ++) {        if( G[v][i] > 0 && Visited[i] == 0) {    //必须是依然有容量的边，才可以走     Prev[i] = v;     Visited[i] = 1;      if( i == m ) {      bFindPath = true;      q.clear();      break;     }     else       q.push_back(i);    }   }  } 
  ^