Nyob rau hauv kev sib piv txoj kev xav tsis yooj yim, kev txo lub sij hawm ntau ntau yog ib txoj hauv kev los daws ib qho teeb meem siv lwm qhov. Polynomial-lub sij hawm txo yog nquag siv nyob rau hauv complexity txoj kev xav rau kev txhais ob complexity chav kawm ntawv thiab ua kom tiav cov teeb meem rau cov chav kawm ntawv. …
Yuav ua li cas yog lub sijhawm polynomial?
Ib qho algorithm tau hais tias yog lub sijhawm polynomial yog tias nws lub sijhawm khiav yog sab saud los ntawm polynomial qhia hauv qhov loj ntawm cov tswv yim rau cov algorithm, uas yog, T(n)=O(nk) rau qee qhov zoo tas li k.
Yuav ua li cas koj thiaj paub yog tias ib yam dab tsi yog lub sijhawm muaj ntau yam?
3 Teb. Ib qho algorithm yog polynomial (muaj lub sijhawm ua haujlwm polynomial) yog rau qee qhov k, C>0, nws lub sijhawm khiav ntawm cov khoom siv ntawm qhov loj n yog feem ntau Cnk. Sib npaug, ib qho algorithm yog polynomial yog rau qee qhov k>0, nws lub sijhawm ua haujlwm ntawm cov khoom siv ntawm qhov loj n yog O(nk).
Yuav ua li cas yog tias qhov txo qis tau tso cai rau lub sijhawm exponential?
Yog tias qhov txo qis tau tso cai rau lub sijhawm nthuav tawm, ces nws tuaj yeem daws qhov teeb meem qub thiab tsim qhov tsis tseem ceeb ntawm lub hom phiaj teeb meem Qhov no txhais tau tias txhua qhov teeb meem hauv NP yog txo tau rau txhua tus. Lwm qhov teeb meem los ntawm hom kev txo qis, yog li txhua qhov teeb meem hauv NP yog NP-ua tiav rau lub sij hawm exponential txo.
Dab tsi yog qhov exponential algorithm?
Ib qho algorithm tau hais tias yog lub sijhawm exponential, if T(n) yog sab saud los ntawm 2poly( ) , qhov twg poly(n) yog qee lub npe hauv n. Ntau yam raug cai, ib qho algorithm yog lub sijhawm exponential yog tias T(n) raug khi los ntawm O(2nk) rau qee qhov tsis tu ncua k. Ref:Wiki.
