分数 2
作者 刘金飞
单位 浙江大学

There are 100000 documents in the database. The statistic data for one query is shown in the following table. The precision is 20%.

Relevant Irrelevant
Retrieved 10000 40000
Not Retrieved 30000 20000

分数 2
作者 Yang Yang
单位 浙江大学

In the master method, we define T(N)T(N) in the recursive form T(N)=aT(N/b)+f(N)T(N) = aT(N/b) + f(N). It means that the algorithm divides the problem into aa parts, with each part being 1b\frac{1}{b} the size of the original. It costs f(N)f(N) to gather results from subproblems and to derive its own result.


分数 2
作者 陈越
单位 浙江大学

A Las Vegas algorithm is a randomized algorithm that always gives the correct result, however the runtime of a Las Vegas algorithm differs depending on the input.
A Monte Carlo algorithm is a randomized algorithm whose output may be incorrect with a certain (typically small) probability. The running time for the algorithm is fixed however.
Then if a Monte Carlo algorithm runs in O(n2)O(n^2) time, with the probability 50% of producing a correct solution, then there must be a Las Vegas algorithm that can get a solution in O(n2)O(n^2) time in expectation.


分数 2
作者 陈昊
单位 浙江大学

To evaluate the prefix-sums of a sequence of 16 numbers by the parallel algorithm with Balanced Binary Trees, C(1,3)C(1,3) is found before C(2,1)C(2,1).

C(h,i)=k=1aA(k)C(h,i) = \sum_{k=1}^{a} A(k) where (0,a)(0, a) is the rightmost descendant leaf of node (h,i)(h, i).


分数 2
作者 陈昊
单位 浙江大学

In a Turnpike Reconstruction problem, given the distance set D={1,2,2,3,3,3,5,5,6,8}D = \{ 1, 2, 2, 3, 3, 3, 5, 5, 6, 8 \}, there must be a point placed at 6.


分数 2
作者 叶德仕
单位 浙江大学

Suppose we have a potential function Φ\Phi such that for all Φ(Di)Φ(D0)\Phi(D_i) \geq \Phi(D_0) for all ii, but Φ(D0)0\Phi(D_0) \neq 0. Then there exists a potential Φ\Phi^\prime such that Φ(D0)=0\Phi ^\prime(D_0) =0, Φ(Di)0\Phi ^\prime(D_i) \geq 0 for all i1i \geq 1, and the amortized costs using Φ\Phi^\prime are the same as the amortized costs using Φ\Phi.


分数 2
作者 陈越
单位 浙江大学

Suppose that TT is an minimum spanning tree of the graph GG, and SS is a connected sub-graph of GG. Then TST\cap S must belong to an minimum spanning tree of SS.


分数 2
作者 卜佳俊
单位 浙江大学

Considering leftist heaps of nn nodes, the Merge operation has a higher time complexity than the DeleteMin operation.


分数 2
作者 卜佳俊
单位 浙江大学

The height of an AVL tree of 30 nodes can be 5. (The height of an empty tree is defined to be -1)


分数 2
作者 丁尧相
单位 浙江大学

NP-complete problems are the hardest problems in NP-hard problems in terms of computational complexity.


分数 2
作者 丁尧相
单位 浙江大学

For an approximation algorithm for a minimization problem, given that the algorithm does not guarantee to find the optimal solution, the best approximation ratio possible to achieve is a constant α>1\alpha > 1.


分数 2
作者 叶德仕
单位 浙江大学

Suppose that the replacement selection is applied to generate longer runs with a priority queue of size 3. Given the sequence of numbers { 81, 94, 11, 96, 12, 99, 17,35,28, 58, 41,75,15}. Then 99 will belong to the 1st run.


分数 2
作者 王灿
单位 浙江大学

Without any assumptions on the distances, if P \neq NP, there is no ρρ-approximation for TSP (Travelling Salesman Problem) for any ρ1ρ \ge 1.