想跟大家请教ETS提供范例中的几题 (题目可以到http://www.ets.org/Media/Tests/GRE/pdf/CompSci.pdf 下载) Consider the collection of all undirected graphs with 10 nodes and 6 edges. Let M and m, respectively, be the maximum and minimum number of connected components in any graph in the collection. If a graph has no selfloops and there is at most one edge between any pair of nodes, which of the following is true? (A) M = 10, m = 10 (B) M = 10, m = 1 (C) M = 7, m = 4 (D) M = 6, m = 4 (E) M = 6, m = 3 Ans: C 这题看不懂. 题目说有6个edges, 那又怎麽可能"one edge between any pair of nodes" In order to find a solution x* to the equation f(x) = 0 for a polynomial f(x) of degree >= 2 with derivative f'(x*) <> 0, Newton’s method does iterations of the form x_(t+1) = x_t - f(x_t)/f'(x_t)' starting with some initial value x_0 <> x* sufficiently close to the desired solution x* to ensure convergence to x*. For fixed values of x_0 and x*, which of the following represents the order of growth of the minimal number of iterations required to compute x* to b bits of accuracy as a function of b ? (A) O(1) (B) O(loglogb) (C) O(logb) (D) O(b^0.5) (E) O(b) Ans: C 这题有甚麽方向可以快速理解的吗? Which of the following characteristics of a programming language is best specified using a context-free grammar? (A) Identifier length (B) Maximum level of nesting (C) Operator precedence (D) Type compatibility (E) Type conversion Ans: C Context-free grammar不是可以用来产生(( ))等巢状表示，为何B不是呢？ In systems with support for automatic memory management, a garbage collector typically has the responsibility for reclaiming allocated memory objects whose contents cannot affect any future legal computation. Such objects are identified by determining that they cannot be reached from a root set. Which of the following is NOT part of the root set in a typical garbage collector? (A) Actual parameters of the active procedures (B) Dynamically allocated objects on the heap (C) Global variables of the program (D) Local variables on the call stack (E) Values in machine registers Ans: B 其它选项可以了解，但为何B不是呢?heap是用来做甚麽的？ --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 140.109.23.135