• 沒有找到結果。

判断题 总分: 35 / 35 1-1 答案正确

N/A
N/A
Protected

Academic year: 2021

Share "判断题 总分: 35 / 35 1-1 答案正确"

Copied!
7
0
0

加載中.... (立即查看全文)

全文

(1)

判断题 总分: 35 / 35

1-1 答案正确 得分: 4 / 4

When measuring the relevancy of the answer set, if the precision is low but the recall is high, it means that most of the relevant documents are missing, but most of the retrieved documents are relevant. (4 分)

T F 1-2 答案正确 得分: 3 / 3

In amortized analysis, a good potential function should always assume its minimum at the start of the sequence. (3 分)

T F 1-3 答案正确 得分: 3 / 3

In a red-black tree, the number of rotations in the DELETE operation is O(1).

(3 分)

T F 1-4 答案正确 得分: 4 / 4

Finding the maximum key from a splay tree will result in a tree with its root having no left subtree. (4 分)

T F 1-5 答案正确 得分: 4 / 4

In an AVL tree, it is possible to have this situation that the balance factors of a node and both of its children are all +1. (4 分)

T F 1-6 答案正确 得分: 3 / 3

Making

N

insertions into an initally empty binomial queue takes

Θ(NlogN)

time in the worst case. (3 分) T F

1-7 答案正确 得分: 3 / 3

The time bound of the FIND operation in a B+ tree containing

N

numbers is

O(lonN)

, no matter what the degree of the tree is. (3 分) T F

1-8 答案正确 得分: 3 / 3

(2)

In backtracking, if different solution spaces have different sizes, start testing from the partial solution with the largest space size would have a better chance to reduce the time cost. (3 分)

T F 1-9 答案正确 得分: 4 / 4

A perfectly balanced tree forms if keys 1 to

2k−1

are inserted in order into an initally empty skew heap. (4 分)

T F 1-10 答案正确 得分: 4 / 4

For the recurrence equation

T(N)=aT(N/b)+f(N)

, if

af(N/b)=f(N)

, then

T(N)=Θ(f(N)logbN)

. (4 分)

T F

选择题 总分: 35 / 40

2-1 答案正确 得分: 5 / 5

A queue can be implemented by using two stacks

SA

and

SB

as follows:

 To enqueue

x

, we push

x

onto

SA

.

 To dequeue from the queue, we pop and return the top item from

SB

.

However, if

SB

is empty, we first fill it (and empty

SA

) by popping the top item from

SA

, pushing this item onto

SB

, and repeat until

SA

is empty.

Assuming that push and pop operations take

O(1)

worst-case time, please select a potential function

ϕ

which can help us prove that enqueue and dequeue

operations take

O(1)

amortized time (when starting from an empty queue). (5 分)

1.

ϕ=2∣SA∣

2.

ϕ=∣SA∣

3.

ϕ=2∣SB∣

4.

ϕ=∣SB∣

2-2 答案正确 得分: 5 / 5

Given the following game tree, which node in the right subtree is the first node to be pruned with α-β pruning algorithm? (5 分)

(3)

1. d 2. a 3. c 4. b

2-3 答案正确 得分: 5 / 5

3-way-mergesort : Suppose instead of dividing in two halves at each step of the mergesort, we divide into three one thirds, sort each part, and finally combine all of them using a three-way-merge. What is the overall time complexity of this algorithm ? (5 分)

1.

O(n)

2.

O(n(log2n))

3.

O(n2logn)

4.

O(nlogn)

2-4 答案正确 得分: 5 / 5

For the result of accessing 9 in the splay tree in the following figure, besides saying that 9 must be the root, which one of the following statements is also TRUE? (5 分)

(4)

1. 12 and 21 are siblings 2. 4 and 21 are siblings 3. 12 is a leaf node 4. 8 and 21 are siblings

2-5 答案错误 得分: 0 / 5

Delete a node

v

from an AVL tree

T1

, we can obtain another AVL tree

T2

. Then

insert

v

into

T2

, we can obtain another AVL tree

T3

. Which one(s) of the following statements about

T1

and

T3

is(are) true? (5 分)

 I、If

v

is a leaf node in

T1

, then

T1

and

T3

might be different.

 II、If

v

is not a leaf node in

T1

, then

T1

and

T3

must be different.

 III、If

v

is not a leaf node in

T1

, then

T1

and

T3

must be the same.

1. I and II only 2. I and III only 3. I only

4. II only

2-6 答案正确 得分: 5 / 5

Insert { 3, 1, 4, 5, 0, 9, 2, 6, 8, 7 } into an initially empty 2-3 tree (with splitting). Which one of the following statements is FALSE? (5 分)

(5)

1. 6 and 7 are in the same node 2. there are 5 leaf nodes

3. the first key stored in the root is 6

4. the parent of the node containing 5 has 3 children

2-7 答案正确 得分: 5 / 5

There are 28000 documents in the database. The statistic data for one query are shown in the following table. The recall is: __ (5 分)

Relevant Irrelevant

Retrieved 4000 12000

Not Retrieved 8000 4000

1. 25%

2. 14%

3. 33%

4. 50%

2-8 答案正确 得分: 5 / 5

Merge the two skew heaps in the following figure. Which one of the following statements is FALSE? (5 分)

1. the null path length of 6 is the same as that of 2 2. 1 is the root with 3 being its right child

3. 5 is the right child of 4

4. Along the left most path from top down, we have 1, 2, 6, and 8

程序填空题 总分: 25 / 25

(6)

5-1 答案正确 得分: 10 / 10

The functions BinQueue_Find and Recur_Find are to find X in a binomial queue H. Return the node pointer if found, otherwise return NULL.

BinTree BinQueue_Find( BinQueue H, ElementType X ) {

BinTree T, result = NULL;

int i, j;

for( i=0, j=1; j<=H->CurrentSize; i++, j*=2) { /* for each tree in H */

T= H->TheTrees[i];

if ( X >=T->Elem ent

(10 分) ){ /* if need to search inside this tree */

result = Recur_Find(T, X);

if ( result != NULL ) return result;

} }

return result;

}

BinTree Recur_Find( BinTree T, ElementType X ) {

BinTree result = NULL;

if ( X==T->Element ) return T;

if ( T->LeftChild!=N U ){

result = Recur_Find(T->LeftChild, X);

if ( result!=NULL ) return result;

}

if ( T->NextSibling!=NULL )

result = Recur_Find(T->NextSibling, X);

return result;

}

分数组成 结果 得分

1 答案正确 5

2 答案正确 5

5-2 答案正确 得分: 15 / 15 IsRBTree (3)

The functions IsRBTree is to check if a given binary search tree T is a red- black tree. Return true if T is, or false if not.

The red-black tree structure is defined as the following:

typedef enum { red, black } colors;

typedef struct RBNode *PtrToRBNode;

struct RBNode{

int Data;

PtrToRBNode Left, Right, Parent;

int BH; /* black height */

colors Color;

};

typedef PtrToRBNode RBTree;

Please fill in the blanks.

bool IsRBTree( RBTree T )

(7)

{

int LeftBH, RightBH;

if ( !T ) return true;

if ( T->Color == black ) T->BH = 1;

else {

if ( T->Left && (T->Left->Color == red)) return false;

if ( T->Right && T->R ight->Color

(15 分) ) return false;

}

if ( !T->Left && !T->Right ) return true;

if ( IsR B Tree(T->R ig ) {

if ( T->Left ) LeftBH = T->Left->BH;

else LeftBH = 0;

if ( T->Right ) RightBH = T->Right->BH;

else RightBH = 0;

if ( LeftBH == RightBH ) { T->B H =LeftB H +T

; return true;

}

else return false;

}

else return false;

}

分数组成 结果 得分

1 答案正确 5

2 答案正确 5

3 答案正确 5

參考文獻

相關文件

However, Venerable Master Hsing Yun said, “Although we have different standpoints and understanding, but for the purpose of propagating the Dharma, we managed to come to

 Definition: A problem exhibits  optimal substructure if an ..

If general metaphysics insists on positing something ‘infinite’, qualitatively different from finite things, and takes it to be the only object worth pursuing, then such a view

• Each student might start from a somewhat different point of view and experience the encounters with works of art and ideas in a different way... Postmodern

Solution: pay attention on the partial input object each time Problem: larger memory implies more parameters in RNN. Solution: long-term memory increases memory size without

• Since the term structure has been upward sloping about 80% of the time, the theory would imply that investors have expected interest rates to rise 80% of the time.. • Riskless

Freely write an added part to the original motive, make sure your new part is of a different duration to the ostinato motive (say, more than two bars in length) so that they have

Schools implementing small class teaching may have different sizes of grouping and different numbers of groups subject to the learning objectives and students’ needs.. The number