data structures - Optimal solution for the "celebrity" algorithm -


among n persons,a "celebrity" defined who known not know anyone. problem identify celebrity, if 1 exists, asking question of form, "excuse me, know person on there?" (the assumption answers correct, , celebrity answer.) goal minimize number of questions.

is there solution of order less obvious o(n^2) here?

using analysis of celebrity problem here

brute-force solution. graph has @ n(n-1) edges, , can compute asking question each potential edge. @ point, can check whether vertex sink computing indegree , outdegree. brute-force solution asks n(n-1) questions. next show how to @ 3(n-1) questions , linear place.

an elegant solution. our algorithm consists of 2 phases: in elimination phase, eliminate 1 person being celebrity; in verification phase check whether 1 remaining person indeed celebrity. elimination phase maintains list of possible celebrities. contains n people. in each iteration, delete 1 person list. exploit following key observation: if person 1 knows person 2, person 1 not celebrity; if person 1 not know person 2, person 2 not celebrity. thus, asking person 1 if knows person 2, can eliminate either person 1 or person 2 list of possible celebrities. can use idea repeatedly eliminate people one, person p. verify brute force whether p celebrity: every other person i , ask person p whether knows person i , , ask persons i whether know person p . if person p answers no, , other people answer yes, declare person p celebrity. otherwise, conclude there no celebrity in group.


-

Popular posts from this blog

c# - ODP.NET Oracle.ManagedDataAccess causes ORA-12537 network session end of file -

overview i want replace oracle.dataaccess orcale. managed dataaccess, opening connection latter throws ora-12537 network session end of file exception. exception message / stack trace {oracleinternal.network.networkexception (0x000030f9): ora-12537 : netzwerksession: dateiende @ oracleinternal.network.readerstream.read(orabuf ob) @ oracleinternal.ttc.orabufreader.getdatafromnetwork() @ oracleinternal.ttc.orabufreader.read(boolean bignoredata) @ oracleinternal.ttc.marshallingengine.unmarshalub1(boolean bignoredata) @ oracleinternal.ttc.ttcprotocolnegotiation.readresponse()} i trying connect oracle 11g database , not have client installed on local machine. working test application (unmanaged) using oracle.dataaccess works fine . using system; using oracle.dataaccess.client; namespace app.odp.unmanaged { internal class program { private static void main(string[] args) { //dummy connection string...
Read more

utf 8 - split utf-8 string into bytes in python -

i trying split utf-8 string bytes in python 3. problem is, when use bytearray, byte, encode etc functions array size of element 14 bytes, not 1 byte expected. need split text file sequence of bytes , send them byte after byte using sockets. tried this: infile = open (file, "r") str = infile.read() byte_str = bytes(str, 'utf-8') print("size of byte_str",sys.getsizeof(byte_str[0])) print gives me 14, need 1... suggestion? quoting official documentation : sys.getsizeof(object[, default]) return size of object in bytes. object can type of object. built-in objects return correct results, not have hold true third-party extensions implementation specific. only memory consumption directly attributed object accounted for, not memory consumption of objects refers to. if given, default returned if object not provide means retrieve size. otherwise typeerror raised. getsizeof() calls object’s __sizeof__ method , adds ...
Read more

matlab - Compression and Decompression of ECG Signal using HUFFMAN ALGORITHM -

i want compress , decompress ecg signal stored text message text file , find out file size, cr,prd ratio,and qs. here code compression , decompression of ecg signal using huffman algorithm. i'm trying find out file size, compression ratio,prd ratio,qs. but error i'm getting the ecg file in text format. %clearing variables , screen enter code here clear all; close all; clc; [file1]=uigetfile('*.txt'); %fprintf('enter ecg file name :%s',file1); p=file1; t=sprintf('%s',p); b1=dlmread([file1]); len=length(b1); lead=input('enter lead number :'); %lead=str2double(lead); col2=b1(1:end,lead); e=fix(sqrt(len)); m=1; i=1:e j=1:e g2(i,j)=fix(col2(m)*1000); %amplifying 1000 m=m+1; end end g3=g2; i=1:e j=1:e ...
Read more