【单选题】施工图预算审查方法中,审查效果好但审查时间较长的方法是( )。
【简答题】若一个n级排列作了奇数次对换后变成了排列123....n,则原来这个排列的逆序数为 。
【单选题】Choose the best way to approach the guest in the following situation. You are asking a guest to wait 15 minutes until his room is ready. You say:
A.
Sir, it will be 15 minutes until your room is ready. Would you like to take a seat, and I will order you a tea or coffee.
B.
You have to wait for 15 minutes.
C.
I'm sorry, Sir. It will be 15 minutes until your room is ready.
【简答题】若排列 的逆序数为 ,则 的逆序数为 .
【单选题】Choose the best way to approach the guest in the following situation. The guest has a choice of potato to go with his steak. You say:
A.
What would you like? Fries or baked potato?
B.
That comes with either fries or baked potato. Which would you prefer?
C.
You can have fries or baked potato.
【判断题】二阶和三阶行列式每一项前面的符号可以这样定,先把每一项因子中的行下标按自然数排列,然后计算列下标的逆序数,奇排列取负号,偶排列取正号。由此猜测: n阶行列式中每项的符号在行下标为自然排列的前提下,若列下标排列为奇排列,则取负号,否则偶排列取正号。
【简答题】任何排列均可通过施行若干次对换化为标准排列,设排列 的逆序数为 t ,可以通过 m 次对换将其化为标准排列,则 t 与 m 的关系为 _______________ 。
【单选题】What makes the situation of having a conversation with the guest more complicated for the doorman?
C.
Their social position.
D.
Their different cultures.
【简答题】在m(m≥2)个不同数的排列P 1 P 2 …P n 中,若1≤i<j≤m时P i >P j (即前面某数大于后面某数),则称P i 与P j 构成一个逆序,一个排列的全部逆序的总数称为该排列的逆序数。记排列(n+1)n(n-1)…321的逆序数为a n ,如排列21的逆序数a 1 =1,排列321的逆序数a 3 =6。 (1)求a 4 、a 5 ,并写出a n 的表达式; (2)令 ,证明2n<...