{"id":"https://openalex.org/W2098367498","doi":"https://doi.org/10.1142/s0218195992000160","title":"THE TWO GUARDS PROBLEM","display_name":"THE TWO GUARDS PROBLEM","publication_year":1992,"publication_date":"1992-09-01","ids":{"openalex":"https://openalex.org/W2098367498","doi":"https://doi.org/10.1142/s0218195992000160","mag":"2098367498"},"language":"en","primary_location":{"id":"doi:10.1142/s0218195992000160","is_oa":false,"landing_page_url":"https://doi.org/10.1142/s0218195992000160","pdf_url":null,"source":{"id":"https://openalex.org/S25827807","display_name":"International Journal of Computational Geometry & Applications","issn_l":"0218-1959","issn":["0218-1959","1793-6357"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310319815","host_organization_name":"World Scientific","host_organization_lineage":["https://openalex.org/P4310319815"],"host_organization_lineage_names":["World Scientific"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"International Journal of Computational Geometry & Applications","raw_type":"journal-article"},"type":"article","indexed_in":["crossref"],"open_access":{"is_oa":false,"oa_status":"closed","oa_url":null,"any_repository_has_fulltext":false},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5060426722","display_name":"Christian Icking","orcid":null},"institutions":[{"id":"https://openalex.org/I120691247","display_name":"FernUniversit\u00e4t in Hagen","ror":"https://ror.org/04tkkr536","country_code":"DE","type":"education","lineage":["https://openalex.org/I120691247"]}],"countries":["DE"],"is_corresponding":true,"raw_author_name":"CHRISTIAN ICKING","raw_affiliation_strings":["Praktische Informatik VI, Fernuniversit \u00e4 t \u2014 GH \u2014 Hagen, Elberfelder Str. 95, D-5800 Hagen, Germany"],"raw_orcid":null,"affiliations":[{"raw_affiliation_string":"Praktische Informatik VI, Fernuniversit \u00e4 t \u2014 GH \u2014 Hagen, Elberfelder Str. 95, D-5800 Hagen, Germany","institution_ids":["https://openalex.org/I120691247"]}]},{"author_position":"last","author":{"id":"https://openalex.org/A5109226564","display_name":"Rolf Klein","orcid":null},"institutions":[{"id":"https://openalex.org/I120691247","display_name":"FernUniversit\u00e4t in Hagen","ror":"https://ror.org/04tkkr536","country_code":"DE","type":"education","lineage":["https://openalex.org/I120691247"]}],"countries":["DE"],"is_corresponding":false,"raw_author_name":"ROLF KLEIN","raw_affiliation_strings":["Praktische Informatik VI, Fernuniversit \u00e4 t \u2014 GH \u2014 Hagen, Elberfelder Str. 95, D-5800 Hagen, Germany"],"raw_orcid":null,"affiliations":[{"raw_affiliation_string":"Praktische Informatik VI, Fernuniversit \u00e4 t \u2014 GH \u2014 Hagen, Elberfelder Str. 95, D-5800 Hagen, Germany","institution_ids":["https://openalex.org/I120691247"]}]}],"institutions":[],"countries_distinct_count":1,"institutions_distinct_count":2,"corresponding_author_ids":["https://openalex.org/A5060426722"],"corresponding_institution_ids":["https://openalex.org/I120691247"],"apc_list":null,"apc_paid":null,"fwci":1.3371,"has_fulltext":false,"cited_by_count":70,"citation_normalized_percentile":{"value":0.79985806,"is_in_top_1_percent":false,"is_in_top_10_percent":false},"cited_by_percentile_year":{"min":89,"max":97},"biblio":{"volume":"02","issue":"03","first_page":"257","last_page":"285"},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T10996","display_name":"Computational Geometry and Mesh Generation","score":0.993399977684021,"subfield":{"id":"https://openalex.org/subfields/1704","display_name":"Computer Graphics and Computer-Aided Design"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},"topics":[{"id":"https://openalex.org/T10996","display_name":"Computational Geometry and Mesh Generation","score":0.993399977684021,"subfield":{"id":"https://openalex.org/subfields/1704","display_name":"Computer Graphics and Computer-Aided Design"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T10374","display_name":"Advanced Graph Theory Research","score":0.9733999967575073,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T10720","display_name":"Complexity and Algorithms in Graphs","score":0.9049000144004822,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/combinatorics","display_name":"Combinatorics","score":0.7926214933395386},{"id":"https://openalex.org/keywords/mathematics","display_name":"Mathematics","score":0.7719718217849731},{"id":"https://openalex.org/keywords/simple-polygon","display_name":"Simple polygon","score":0.7335907220840454},{"id":"https://openalex.org/keywords/polygon","display_name":"Polygon (computer graphics)","score":0.7139517068862915},{"id":"https://openalex.org/keywords/plane","display_name":"Plane (geometry)","score":0.5701128244400024},{"id":"https://openalex.org/keywords/boundary","display_name":"Boundary (topology)","score":0.5645643472671509},{"id":"https://openalex.org/keywords/binary-logarithm","display_name":"Binary logarithm","score":0.4946272075176239},{"id":"https://openalex.org/keywords/simple","display_name":"Simple (philosophy)","score":0.48387181758880615},{"id":"https://openalex.org/keywords/space","display_name":"Space (punctuation)","score":0.4624505341053009},{"id":"https://openalex.org/keywords/time-complexity","display_name":"Time complexity","score":0.45937761664390564},{"id":"https://openalex.org/keywords/discrete-mathematics","display_name":"Discrete mathematics","score":0.35044246912002563},{"id":"https://openalex.org/keywords/monotone-polygon","display_name":"Monotone polygon","score":0.25154751539230347},{"id":"https://openalex.org/keywords/geometry","display_name":"Geometry","score":0.17374572157859802},{"id":"https://openalex.org/keywords/computer-science","display_name":"Computer science","score":0.10722735524177551},{"id":"https://openalex.org/keywords/mathematical-analysis","display_name":"Mathematical analysis","score":0.10484766960144043}],"concepts":[{"id":"https://openalex.org/C114614502","wikidata":"https://www.wikidata.org/wiki/Q76592","display_name":"Combinatorics","level":1,"score":0.7926214933395386},{"id":"https://openalex.org/C33923547","wikidata":"https://www.wikidata.org/wiki/Q395","display_name":"Mathematics","level":0,"score":0.7719718217849731},{"id":"https://openalex.org/C197949415","wikidata":"https://www.wikidata.org/wiki/Q782746","display_name":"Simple polygon","level":3,"score":0.7335907220840454},{"id":"https://openalex.org/C190694206","wikidata":"https://www.wikidata.org/wiki/Q3276654","display_name":"Polygon (computer graphics)","level":3,"score":0.7139517068862915},{"id":"https://openalex.org/C17825722","wikidata":"https://www.wikidata.org/wiki/Q17285","display_name":"Plane (geometry)","level":2,"score":0.5701128244400024},{"id":"https://openalex.org/C62354387","wikidata":"https://www.wikidata.org/wiki/Q875399","display_name":"Boundary (topology)","level":2,"score":0.5645643472671509},{"id":"https://openalex.org/C63553672","wikidata":"https://www.wikidata.org/wiki/Q581168","display_name":"Binary logarithm","level":2,"score":0.4946272075176239},{"id":"https://openalex.org/C2780586882","wikidata":"https://www.wikidata.org/wiki/Q7520643","display_name":"Simple (philosophy)","level":2,"score":0.48387181758880615},{"id":"https://openalex.org/C2778572836","wikidata":"https://www.wikidata.org/wiki/Q380933","display_name":"Space (punctuation)","level":2,"score":0.4624505341053009},{"id":"https://openalex.org/C311688","wikidata":"https://www.wikidata.org/wiki/Q2393193","display_name":"Time complexity","level":2,"score":0.45937761664390564},{"id":"https://openalex.org/C118615104","wikidata":"https://www.wikidata.org/wiki/Q121416","display_name":"Discrete mathematics","level":1,"score":0.35044246912002563},{"id":"https://openalex.org/C2834757","wikidata":"https://www.wikidata.org/wiki/Q4925424","display_name":"Monotone polygon","level":2,"score":0.25154751539230347},{"id":"https://openalex.org/C2524010","wikidata":"https://www.wikidata.org/wiki/Q8087","display_name":"Geometry","level":1,"score":0.17374572157859802},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.10722735524177551},{"id":"https://openalex.org/C134306372","wikidata":"https://www.wikidata.org/wiki/Q7754","display_name":"Mathematical analysis","level":1,"score":0.10484766960144043},{"id":"https://openalex.org/C111919701","wikidata":"https://www.wikidata.org/wiki/Q9135","display_name":"Operating system","level":1,"score":0.0},{"id":"https://openalex.org/C111472728","wikidata":"https://www.wikidata.org/wiki/Q9471","display_name":"Epistemology","level":1,"score":0.0},{"id":"https://openalex.org/C76155785","wikidata":"https://www.wikidata.org/wiki/Q418","display_name":"Telecommunications","level":1,"score":0.0},{"id":"https://openalex.org/C126042441","wikidata":"https://www.wikidata.org/wiki/Q1324888","display_name":"Frame (networking)","level":2,"score":0.0},{"id":"https://openalex.org/C138885662","wikidata":"https://www.wikidata.org/wiki/Q5891","display_name":"Philosophy","level":0,"score":0.0}],"mesh":[],"locations_count":2,"locations":[{"id":"doi:10.1142/s0218195992000160","is_oa":false,"landing_page_url":"https://doi.org/10.1142/s0218195992000160","pdf_url":null,"source":{"id":"https://openalex.org/S25827807","display_name":"International Journal of Computational Geometry & Applications","issn_l":"0218-1959","issn":["0218-1959","1793-6357"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310319815","host_organization_name":"World Scientific","host_organization_lineage":["https://openalex.org/P4310319815"],"host_organization_lineage_names":["World Scientific"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"International Journal of Computational Geometry & Applications","raw_type":"journal-article"},{"id":"pmh:oai:CiteSeerX.psu:10.1.1.24.2959","is_oa":false,"landing_page_url":"http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.24.2959","pdf_url":null,"source":null,"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"http://wwwpi6.fernuni-hagen.de/Publikationen/ik-tgp-92.pdf","raw_type":"text"}],"best_oa_location":null,"sustainable_development_goals":[],"awards":[],"funders":[],"has_content":{"pdf":false,"grobid_xml":false},"content_urls":null,"referenced_works_count":0,"referenced_works":[],"related_works":["https://openalex.org/W2608536130","https://openalex.org/W2102467404","https://openalex.org/W2987051945","https://openalex.org/W2154329468","https://openalex.org/W53644101","https://openalex.org/W4296464845","https://openalex.org/W2389833224","https://openalex.org/W2372903818","https://openalex.org/W1567510565","https://openalex.org/W2109630252"],"abstract_inverted_index":{"Given":[0],"a":[1,34,69],"simple":[2],"polygon":[3],"in":[4,32,46,53],"the":[5,24,59,64,82,85],"plane":[6],"with":[7],"two":[8,18,25],"distinguished":[9],"vertices,":[10],"s":[11,29],"and":[12,52,87],"g,":[13],"is":[14,58,81,92],"it":[15],"possible":[16],"for":[17],"guards":[19],"to":[20,30],"simultaneously":[21],"walk":[22,70],"along":[23],"boundary":[26],"chains":[27],"from":[28],"g":[31],"such":[33],"way":[35],"that":[36,90],"they":[37],"are":[38],"always":[39],"mutually":[40],"visible?":[41],"We":[42],"decide":[43],"this":[44,91],"question":[45],"time":[47,75],"O":[48],"(n":[49],"log":[50,77],"n)":[51],"linear":[54],"space,":[55],"where":[56,79],"n":[57],"number":[60],"of":[61,63,71,84],"edges":[62],"polygon.":[65],"Moreover,":[66],"we":[67,88],"compute":[68],"minimum":[72],"length":[73],"within":[74],"O(n":[76],"n+k),":[78],"k":[80],"size":[83],"output,":[86],"prove":[89],"optimal.":[93]},"counts_by_year":[{"year":2022,"cited_by_count":1},{"year":2021,"cited_by_count":1},{"year":2019,"cited_by_count":1},{"year":2015,"cited_by_count":1},{"year":2014,"cited_by_count":1},{"year":2013,"cited_by_count":2},{"year":2012,"cited_by_count":3}],"updated_date":"2026-05-21T06:26:12.895304","created_date":"2025-10-10T00:00:00"}