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CS 245
Definitions
132
Computer Science
Undergraduate 2
05/02/2007

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Term
Discrete Mathematics
Definition
encompasses the representation and study of collections of distinct objects
Term
Philosophical Logic
Definition
is the classical notion of ‘logic:’ The study of thought and reasoning
Term
Mathematical Logic
Definition
is the use of formal languages and grammars to represent the syntax and semantics of computation
Term
A Well-Formed Formula (wff)
Definition
is a correctly structured expression of a language
Term
A proposition (a.k.a. statement)
Definition
is a claim that is either true or false with respect to an associated
context.
Term
simple proposition
Definition
A proposition that contains no logical operators.
Term
compound proposition.
Definition
A claim that is a combination of multiple propositions
Term
Equivalent (p ≡ q)
Definition
Two propositions p and q are (Logically) Equivalent (p ≡ q) when both evaluate to the same result when
presented with the same input
Term
Tautology
Definition
a proposition that always evaluates to true
Term
Contradiction
Definition
a proposition that always evaluates to false
Term
Contingency
Definition
a proposition that is neither a tautology nor a contradiction
Term
Inverse
Definition
The Inverse of p → q is p → q
Term
Converse
Definition
The Converse of p → q is q → p
Term
Contraposition
Definition
The Contraposition of p → q is q → p
Term
(Logically) Equivalent
Definition
p and q are (Logically) Equivalent, written p ≡ q, if p ↔ q is a tautology
Term
Predicate (a.k.a. Propositional Function)
Definition
A statement that includes one or more variables and will evaluate to either true or false when the variables
are assigned values
Term
Domain of Discourse
(a.k.a. Universe of Discourse)
Definition
The collection of values from which a variable’s value is drawn is known as the
Term
Bound variable
Definition
A quantified variable in a predicate
Term
Free (a.k.a. Unbound) variables
Definition
Unquantified variables
Term
An Argument
Definition
connected series of statements to establish a definite proposition
Term
Inductive Argument.
Definition
An argument that moves from specific observations to a general conclusion
Term
Deductive Argument
Definition
An argument that uses accepted general principles to explain a specific situation
Term
Valid argument
Definition
Any deductive argument of the form (p1 ^ p2 ^ . . . ^ pn) → q is Valid if the conclusion must follow from the hypotheses
Term
Sound argument
Definition
A valid argument that also has true premises
Term
Fallacy
Definition
an argument constructed with an improper inference
Term
Conjecture
Definition
a statement with an unknown truth value
Term
Theorem
Definition
conjecture that has been shown to be true
Term
Proof
Definition
A sound argument that establishes the truth of a theorem
Term
Lemma
Definition
a simple theorem whose truth is used to construct more complex theorems
Term
Corollary
Definition
a theorem whose truth follows directly from another theorem
Term
set
Definition
an unordered collection of unique objects
Term
subset
Definition
Set A is a subset of set B (written A ⊆B) if every member of A can be found in B.
Term
proper subset
Definition
A is a proper subset of B (written A ⊂ B) if A ⊆B and A != B
Term
Power set
Definition
power set of a set A (written P(A)) is the set of all of A’s subsets, including the empty set cardinality of |P(A)|=2^|A|
Term
disjoint
Definition
Two sets are disjoint if their intersection is ∅
Term
partition
Definition
A partition of a set divides its members into disjoint subsets
Term
ordered pair
Definition
An ordered pair is a group of two items (a, b) such that (a, b) != (b, a) unless a = b
Term
Cartesian Product
Definition
The Cartesian Product (symbol: ×) of two sets A and B is the set of all ordered pairs (a, b) such that
a ∈A and b ∈ B
Term
matrix
Definition
A matrix is an n-dimensional collection of values
Term
Matrix equality
Definition
Two matrices A and B are equal if they share the same dimensions and each pair of corresponding elements is equal.
Term
Matrix Symmetry
Definition
A matrix A is symmetric if A = AT .
Term
(binary) relation
Definition
A (binary) relation from set X to set Y is a subset of the Cartesian Product of the domain X and the codomain Y .
Term
Reflexive
Definition
A relation R on set A is reflexive if (a, a) ∈ R, ∀a ∈ A.
Term
symmetric
Definition
A relation R on set A is symmetric if (a, b) ∈ R whenever (b, a) ∈ R for a, b ∈ A.
Term
antisymmetric
Definition
A relation R on set A is antisymmetric if (x, y) ∈ R and x != y, then (y, x) ∉ R, ∀x, y ∈ A.
Term
transitive
Definition
A relation R on set A is transitive if whenever (a, b) ∈ R and (b, c) ∈ R, then (a, c) ∈R, for a, b, c ∈ A
Term
Inverse of relation
Definition
The inverse of a relation R, denoted R−1, contains all of the ordered pairs of R with their components
exchanged. (That is, R−1 = {(b, a) | (a, b) ∈ R}.)
Term
composite
Definition
Let G be a relation from set A to set B, and let F be a relation from B to set C. The composite of F and G, denoted F ◦ G, is the relation of ordered pairs (a, c), a ∈A, c ∈C, such that b ∈ B, (a, b) ∈ G and (b, c) ∈ F
Term
weak partial order
Definition
A relation R on set A is a (reflexive/weak) partial order if it is reflexive, antisymmetric, and transitive
Term
irreflexive
Definition
A relation R on set A is irreflexive if for all members of A, (a, a) ∉ R
Term
Strict partial order
Definition
A relation R on set A is an irreflexive (or strict) partial order if it is irreflexive, antisymmetric, and
transitive.
Term
equivalence relation
Definition
A relation R on set A is an equivalence relation if it is reflexive, symmetric, and transitive.
Term
equivalence class
Definition
denoted [b], of an element b ∈ B and an equivalence relation R on B is {c ∈ B |
(b, c) ∈ R}. That is, the equivalence class is the set of all elements of the base relation equivalent to a
given element as defined by the relation.
Term
Comparable
Definition
Let R be a partial order on set A. a and b are said to be comparable if a, b ∈ A and either a ≼ b or b ≼ a
(that is, (a, b) ∈ R or (b, a) ∈ R).
Term
Total order
Definition
• A partially-ordered relation R on set A is a total order if every pair of elements a, b ∈ A are comparable.
Term
Function
Definition
A function from set X to set Y , denoted f : X → Y , is a relation from X to Y . If (x, y) ∈ f, then y is
the only value returned from f(x). Further, f(x) is defined ∀x ∈ X
Term
let f : X → Y be a function, and assume f(n) = p
domain
codomain
mapping
image
pre-image
range
Definition
• For each of the following,.
– X is the domain of f.
– Y is the codomain of f.
– f maps X to Y .
– p is the image of n.
– n is the pre-image of p.
– The range of f is the set of all images of elements of X. (Note that the range need not equal the
codomain.)
Term
Injective
Definition
A function f : X → Y is injective (a.k.a. one-to-one) if, for each y ∈Y , f(x) = y for at most one
member of X
Term
Surjective
Definition
A function f : X → Y is surjective (a.k.a. onto) if f’s range is Y (the range = the codomain).
Term
A bijective function
Definition
(a.k.a. a one-to-one correspondence) is both injective and surjective
Term
inverse of function
Definition
inverse of a bijective function f, denoted f−1, is the relation {(y, x) | (x, y) ∈ f}
Term
function composition
Definition
Let f : Y → Z and g : X → Y . The composition of f and g, denoted f ◦ g, is the function h = f(g(x)),
where h : X → Z.
Term
binary function
Definition
A function f : X x Y → Z (or f(x, y) = z) is a binary function
Term
prime
Definition
A positive integer p is prime if p ≥ 2 and the only factors of p are 1 and p
Term
composite
Definition
A positive integer p is composite if p ≥ 2 and p is not prime
Term
Greatest common Divisor
Definition
Let x and y be integers such that x != 0 and y != 0. The Greatest Common Divisor (GCD) of x and y is the largest integer i such that i | x and i | y. That is, gcd(x,y) = i.
Term
Relatively prime & pairwise Relatively prime
Definition
If the GCD of a and b is 1, then a and b are relatively prime
_________________________________________

When the members of a set of integers are all relatively prime to one another, they are pairwise relatively
prime
Term
Least common multiple
Definition
Let x and y be positive integers. The Least Common Multiple (LCM) of x and y is the smallest integer
s such that x | s and y | s. That is, lcm(x,y) = s
Term
congruent modulo m
Definition
If a, b ∈Z and m ∈ Z+, then a and b are congruent modulo m (written a ≡ b (mod m)) iff a%m = b%m
(or, iff m| (a − b)).
Term
Sequence
Definition
A sequence is the ordered range of a function from a set of integers to a set S.
Term
In an arithmetic sequence (a.k.a. arithmetic progression)
Definition
a, |an+1 − an| is constant. This constant is called the common difference of the sequence.
Term
geometric sequence (a.k.a. geometric progression)
Definition
g, gn+1/gn is constant. This constant is called the common ratio of the sequence
Term
subsequence
Definition
A subsequence is a sequence formed from a subset of the elements of another sequence in which relative element order is retained
Term
String
Definition
a contiguous finite sequence of zero or more elements drawn from a set called the alphabet.
Term
Finite sequence
Definition
A set is finite if there exists a bijective mapping between it and a set of cardinality n, n ∈ Z*.
Term
countably infinite (a.k.a. denumerably infinite)
Definition
if the bijective mapping is to either of the sets Z* or Z+
Term
Countable
Definition
set is countable if it is either finite or countably infinite. If neither, the set is uncountable
Term
The Principle of Mathematical Induction:
Definition
To prove that P(n) is true for every positive integer n, we
need to show that (1) P(1) is true, and (2) if P(i) is true for all 1 ≤ i ≤ n, then P(n + 1) is true. (1) is
called the basis step, and (2) is known as the inductive step
Term
Strong induction
Definition
P(i) must be true and, for any k ≥ i, if P(i) ∧ P(i + 1) ∧ . . . ∧ P(k − 1) ∧ P(k) is true, then P(k + 1) is true
Term
Weak Induction
Definition
P(i) must be true and, for any k ≥ i, if P(k) is true, then P(k + 1) is true
Term
The (Generalized) Pigeonhole Principle
Definition
that if n items are placed in k boxes, then at least one box contains at least ⌈n/k ⌉ items
Term
The Multiplication Principle (a.k.a. the Product Rule):
Definition
If there are s steps in an activity, with n1 ways
of accomplishing the first step, n2 of accomplishing the second, etc., and ns ways of accomplishing the
last step, then there are n1 xn2 x. . . xns ways to complete all s steps.
Term
The Addition Principle (a.k.a. the Sum Rule):
Definition
If there are t tasks, with n1 ways of accomplishing the
first, n2 ways of accomplishing the second, etc., and nt ways of accomplishing the last, then there are
n1 + n2 + . . . + nt ways to complete one of these tasks, assuming that no two tasks interfere with one
another.
Term
The Principle of Inclusion-Exclusion for Two Sets
Definition
says that the cardinality of the union of sets M and
N is the sum of their individual cardinalities excluding the cardinality of their intersection. That is:
|M ∪ N| = |M| + |N| − |M ∩ N|
Term
The Principle of Inclusion-Exclusion for Three Sets
Definition
says that the cardinality of the union of sets M, N,
and O is the sum of their individual cardinalities excluding the sum of the cardinalities of their pairwise
intersections and including the cardinality of their intersection. That is:
|M ∪ N ∪ O| = |M| + |N| + |O| −(|M ∩ N| + |M ∩ O| + |N ∩ O|) + |M ∩ N ∩ O|
Term
Permutation
Definition
An ordering of n distinct elements is
Term
r-permutation
Definition
An ordering of an r-element subset of n distinct elements
Term
r-combination
Definition
of X = {x1, x2, . . . , xn} is an r element subset of X, denoted C(n, r) or 􀀀n
r_ and read “n choose r”.
Term
algorithm
Definition
a set of instructions for performing a task
Term
recursive definition
Definition
has two (sometimes three) parts:
1. The basis clause determines how trivial cases are to be handled.
2. The inductive clause explains how complex problems are answered in terms of simpler versions of
the same problem.
3. The extremal clause says that only cases covered by the basis and inductive clauses are covered by
the recursive definition. That is, the extremal clause provides boundaries for the definition.
Term
recursive algorithm
Definition
expresses the solution to a task in terms of a simpler case of the same problem
Term
Fibonacci sequence
Definition
The nth term of the Fibonacci sequence is the sum of terms n−1 and n−2, where F(0) = 0 and F(1) = 1
Term
recurrence relation
Definition
A recurrence relation for the sequence a0, a1, . . . is an equation that expresses term ak in terms of one or
more of its preceding sequence members, one of more of which are explicitly stated initial conditions of
the sequence.
Term
A linear homogeneous recurrence relation with constant coefficients
Definition
A linear homogeneous recurrence relation with constant coefficients of degree (or order) k (abbreviated:
LHRRWCC of degree k) has the form R(n) = c1R(n − 1) + c2R(n − 2) + . . . + ckR(n − k), where ci ∈ R
and ck != 0
Term
probability
Definition
The probability that a specific event will occur is the ratio of the number of actual occurrences to the
number of possible occurrences
Term
Addition
Definition
P/∴pvq
Term
Simplification
Definition
p^q/∴p
Term
conjunction
Definition
p,q/∴p^q
Term
modus ponens
Definition
p,p->q/∴q
Term
modus tollens
Definition
~p,p->q/∴~p
Term
hypothetical Syllogism
Definition
p->q,q->r/∴p->r
Term
disjunctive syllogism
Definition
pvq,~p/∴q
Term
Resolution
Definition
pvq,~pvr/∴qvr
Term
names for p and q
Definition
Antecedent -> consequence
Hypothesis -> conclusion
Sufficient -> necessary
Term
wording for conditional proposition
Definition
if p then q
p only if q
q unless ~p
Term
Affirming the conclusion
Definition
p->t
t
______
∴p
Term
Affirming the conclusion
Definition
p->t
t
______
∴p
Term
Denying the hypothesis
Definition
P->t
~p
_____
∴~t
Term
Circular reasoning/ Begging the Question
Definition
...P.../∴P
Term
Universal Instantiation
Definition
∀xP(x),X∈D/∴P(d) d∈D
Term
Universal generalization
Definition
P(d) for any d∈D / ∴ ∀xP(x) , X∈D
Term
Existential Instantiation
Definition
∃xP(x) , X∈D/ ∴P(d) for some d∈D
Term
Existential generalization
Definition
P(d) for some d∈D/∴ ∃xP(x) , X∈D
Term
direct proof
Definition
assume p prove q
Term
contrapositive
Definition
to prove p->q; assume ~q prove ~p
Term
proof by contradiction
Definition
to prove p->q; assume( ~qvp) show a contradiction
Term
join for matrix
Definition
(AvB) Or of corresponding pair of values in a matrix
Term
meet for matrix
Definition
(A^B) And of corresponding matrix element
Term
Division
Definition
quotient(q) dividend(n) divisor(s) remainder(r) n=sxq+r where 0<=r0
Term
Division
Definition
quotient(q) dividend(n) divisor(s) remainder(r) n=sxq+r where 0<=r0
Term
Counting table
Definition
Repetition no repetition
ordered r^n P(n,r)
unordered pips/pipes C(n,r)
C(n+r-1,r)
Term
Computable
Definition
solution can be described by an algorithm
Term
tractable
Definition
Algorithm is efficient(binary search)
Term
intractable
Definition
no efficient solution algorithm is known (playing chess)
Term
non-computable
Definition
no algorithm will ever describe the solution ( halting problem )
Term
characteristics of algorithm
Definition
1) input- data from outside source
2) output- info produced bed execution of algorithm
3) Generality:the instructions can solve a collection of similar problem
4) definiteness: the set of instructions is not open to interpretation
5)correctness- output accepted output for the given input
6) finiteness: the complete output is produced after a finite # of instruction have been executed
Term
GCD property
Definition
GCD(a,b) = GCD(b,a%b)
Term
Two degree LHRRWCC
Definition
an=c1a(n-1)+ c2a(n-2)
characteristic equation:
w^2-c1w-c2=0 solve for W1 & W2
answer:
an=m1W1^n + m2W2^n
or an=m1W^n +m2nW^n when W1=W2
Term
Horn clause
Definition
only or's and at most one non negated term
Term
Masters Theorem
Definition
a recursive funcion in form of
T(n)=aT(n/b)+cn^d
T(n) is increasing n=b^k
a is a real is less then = to 1
b is an integer is less then 1
c is a r number is less then 1
d is a r number is less then = to 0 f(n)= O(n^d) -> a less b^d
f(n)= O(n^dlog2n) -> a=b^d
f(n)= O(n^(logba)) -> a greater b^d
Term
horn clause
Definition
only or's and at most one non negative term
Term
symmetry
Definition
with big theta
if f(n) is big theta of g(n) then g(n) is big theta of f(n)
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