62 lines
2.0 KiB
Python
62 lines
2.0 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# IMPORTS
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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from local.maths import *;
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from local.typing import *;
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from code.core.log import *;
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from code.algorithms.methods import *;
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# GLOBAL VARIABLES/CONSTANTS
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# CHECKS
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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def preChecks(L: List[int], **_):
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assert L == sorted(L), 'Ungültiger Input: L muss aufsteigend sortiert sein!';
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return;
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def postChecks(L: List[int], x: int, index: int, **_):
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value = L[index] if index >= 0 else None;
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assert value == x, 'Der Algorithmus hat versagt.';
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return;
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# ALGORITHM binary search
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# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@algorithmInfos(name='Binärsuchalgorithmus', outputnames='index', checks=True, metrics=True, preChecks=preChecks, postChecks=postChecks)
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def BinarySearch(L: List[int], x: int) -> int:
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'''
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Inputs: L = Liste von Zahlen, x = Zahl.
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Annahme: L sei aufsteigend sortiert.
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Outputs: Position von x in L, sonst −1 wenn x nicht in L.
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'''
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if len(L) == 0:
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logDebug('x nicht in L');
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return -1;
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AddToCounter();
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m = math.floor(len(L)/2);
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if L[m] == x:
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logDebug('x in Position m gefunden');
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return m;
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elif x < L[m]:
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logDebug('Suche in L[0], L[1], ..., L[m] fortsetzen, m = {}.'.format(m));
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index = BinarySearch(L=L[:m], x=x);
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return index;
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else: # x > L[m]
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logDebug('Suche in L[m+1], L[m+2], ..., L[len(L)-1] fortsetzen, m = {}.'.format(m));
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index = BinarySearch(L=L[m+1:], x=x);
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return (m + 1) + index; # NOTE: muss Indexwert kompensieren
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