python 3.x - Why does my binary search use so many comparisons? -


here code:

def binary_search(sortedlist,target,comparisons): start = 0 end = len(sortedlist) - 1   while(end - start >= 0):     mid = (start + end)//2     comparisons += 2     if(target < sortedlist[mid]):         comparisons -= 1         end = mid - 1     elif(target > sortedlist[mid]):         start = mid + 1     else:         return target, comparisons return false, comparisons

it same every other post on here binary searching reason uses way many comparisons.

here code after fixed myself

from classes import genelist ## uncomment following line able make own testing genes # classes import gene, genome  def binary_search(sortedlist, target, comparisons):     reducedlist = sortedlist      while len(reducedlist) > 1:         mid = len(reducedlist) // 2         comparisons += 1         if target < reducedlist[mid]:             reducedlist = reducedlist[:mid]         else:             reducedlist = reducedlist[mid:]      comparisons += 1     if reducedlist[0] == target:         return reducedlist[0], comparisons     else:         return false, comparisons   def genetic_similarity_binary(first_genome, second_genome):     """ function takes 2 genome objects, , returns genelist     , integer. genelist of genes common     between first_genome , second_genome, while integer     how many comparisons took find similar genes.     hint: might pay define helper function.     """     comparisons = 0     similar_list = genelist()     target in first_genome:         result, comparisons = binary_search(second_genome, target, comparisons)         if result:             similar_list.append(result)     return similar_list, comparisons

you dont have middle check

for optimisation purposes, should check termination condition first. try way,

def binary_search(sortedlist,target,comparisons): start = 0 end = len(sortedlist) - 1   while(end - start >= 0):     mid = (start + end)//2     comparisons += 2     if(target == sortedlist[mid]):         comparisons -= 1         return target, comparisons     elif(target > sortedlist[mid]):         start = mid + 1     else:         end = mid - 1 return false, comparisons

as upon execution of binary_search([1,2,3,4,5,6,7,8,9,10],9,0)

for code gives outcome (9, 6) , above mentioned changes give (9, 5)


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj...
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer ...
Read more

c# - Asp.net web api : redirect unauthorized requst to forbidden page -

im trying redirect unauthorized request forbidden page instead i'm getting forbidden page in response body , how can fix ? here's startup class : app.createperowincontext(storecontext.create); app.createperowincontext<applicationusermanager>(applicationusermanager.create); app.createperowincontext<applicationsigninmanager>(applicationsigninmanager.create); app.usecookieauthentication(new cookieauthenticationoptions { authenticationtype = defaultauthenticationtypes.applicationcookie, expiretimespan = timespan.fromdays(30), }); app.useexternalsignincookie(defaultauthenticationtypes.externalcookie); app.usetwofactorsignincookie(defaultauthenticationtypes.twofactorcookie, timespan.fromminutes(5)); app.usetwofactorrememberbrowsercookie(defaultauthenticationtypes.twofactorrememberbrowsercookie); the method im trying reach : [httpget] [authorize(roles = "admin")] public string getcurrentusername() { return userman...
Read more