/in/foo.cc: In function 'int main()':
/in/foo.cc:26:9: error: 'Q' was not declared in this scope
         Q.push(arr[i]) ;//将元素插入队中
         ^
/in/foo.cc:31:16: error: 'Q' was not declared in this scope
         tmp1 = Q.top() ;//取出第一个较小元素
                ^