.
1. .
2. - . "" .
3. , .
, , . , " " , - , "" , . 2) , , , . , , : "" , . , , , "". "", .
. , , . , , , ( ), (, ), .
31
, . .
, , - , .. , . . 10.19, ( ) - . , -, .. .
- , . 10.19, - . , . , , , : () .
|
|
. , , " ". , , (, ) (, D), . 10.20, "" , . . 10.20 , , (, ), D (D, ). (, ) (, D) (, ) (, D), , .1 , D, ~ , , .
.
, NP- .
.
, .
, .
, .
, , , .
----------------------
I Π. sol(I) .
, sol(I) ̸= ∅ I. x ∈ sol(I) cost(x). x ∈ sol(I), cost ( ) . (approximation algorithm)
Π , I - x ∈ sol(I). A(I) , A I.
A (absolute performance guarantee) c, I |OPT(I) − A(I)| ≤ c.
A (relative performance guarantee) 𝛼, I
A(I)/OPT(I) ≥ 𝛼 ;
A(I)/OPT(I) ≤ 𝛼 .
𝛼-.
𝛼 ≤ 1, 𝛼 ≥ 1.
, 𝛼 1.
Π. Π (polynomial time approximation scheme, PTAS),
|
|
1 𝜖 ≥ 0 (1 − 𝜖)- Π;
2 𝜖 > 0 n .
n, 1/𝜖, (fully
polynomial time approximation scheme, FPTAS).
.