题目内容

If we have a magic machine that can solve 3-SAT problem in unit time. Which of the following problem can NOT be solve if we only use this machine polynomial times? (Assume P ≠ NP)

A. INDEPENDENT-SET
B. VERTEX-COVER
C. PRIMES
D. HALTING PROBLEM

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Suppose we are given an instance of the [mathjaxinline]s-t[/mathjaxinline] shortest path problem on a directed graph [mathjaxinline]G[/mathjaxinline]. We assume that all edge cost are positive and distinct. Let [mathjaxinline]P[/mathjaxinline] be a minimum-cost [mathjaxinline]s-t[/mathjaxinline] path for this instance. Now suppose we replace each edge cost [mathjaxinline]c_e [/mathjaxinline] by its square, [mathjaxinline]c_e^2 [/mathjaxinline], thereby creating a new instance of the problem with the same graph but different costs.Decide whether you think the following statement is true or false.[mathjaxinline]P[/mathjaxinline] must still be a minimum-cost [mathjaxinline]s-t[/mathjaxinline] path for this new instance.[mathjaxinline]P[/mathjaxinline] must still be a minimum-cost [mathjaxinline]s-t[/mathjaxinline] path for this new instance.

If we want to proof problem $Y$ can be solved in polynomial-time via a reduction from problem $X$, which of the following statement is NOT necessary?

Arbitrary instances of problem $X$ can be solved in polynomial-time.
B. Arbitrary instances of problem $X$ can be solved using polynomial number of calls to oracle that solves problem $Y$.
C. Arbitrary instances of problem $Y$ can be solved using polynomial number of calls to oracle that solves problem $X$.

1860年率领太平军抗击洋枪队的将领是( )

A. 李秀成
B. 邓世昌
C. 关天培
D. 左宗棠

因为英国侵略缅甸、法国侵略越南,中国西南边境出现危机,( )直接受到威胁。 A广西 B广西

A. 福建 D云南

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