Graph

๊ทธ๋ž˜ํ”„(Graph)๋Š” ์ •์ (Vertex)์˜ ์ง‘ํ•ฉ V์™€ ๊ฐ„์„ (Edge)์˜ ์ง‘ํ•ฉ E๋กœ ๊ตฌ์„ฑ๋œ ๋น„์„ ํ˜• ๋ฐ์ดํ„ฐ ๊ตฌ์กฐ

์ •์ (Vertex) : ์ž๋ฃŒ๋ฅผ ์ €์žฅํ•˜๋ ค๋Š” ์ž๋ฃŒ์˜ ๋‹จ์œ„, ๋…ธ๋“œ(Node)๋ผ๊ณ ๋„ ๋งํ•จ.

๊ฐ„์„ (Edge) : ์ •์  ์‚ฌ์ด๋ฅผ ์—ฐ๊ฒฐํ•˜๋Š” ์„ ์œผ๋กœ ๋‘ ์ •์  ์Œ (u, v)๋กœ ํ‘œํ˜„ํ•จ.

GRAPH

EDGE

๋ฐฉํ–ฅ์„ฑ(์œ ํ–ฅ)

๋ฐฉํ–ฅ์„ ๊ฐ€์ง„ ์ •์ ์˜ ์Œ (u, v)์œผ๋กœ ํ™”์‚ดํ‘œ๋กœ ํ‘œํ˜„ํ•˜๊ณ  ๋‹จ๋ฐฉํ–ฅ์„ ๊ฐ€๋ฆฌํ‚ต๋‹ˆ๋‹ค.

์ฒซ ๋ฒˆ์งธ ์ •์  u๋Š” ์ถœ๋ฐœ์ ์„ ์˜๋ฏธํ•˜๊ณ  ๋‘ ๋ฒˆ์งธ ์ •์  v๋Š” ๋„์ฐฉ์ ์„ ์˜๋ฏธํ•ฉ๋‹ˆ๋‹ค.

๋ฐฉํ–ฅ์„ฑ ๊ฐ„์„ ์„ ๊ฐ€์ง„ ๊ทธ๋ž˜ํ”„๋ฅผ ๋ฐฉํ–ฅ์„ฑ ๊ทธ๋ž˜ํ”„(Directed Graph)๋ผ๊ณ  ํ•ฉ๋‹ˆ๋‹ค.

๋ฌด๋ฐฉํ–ฅ์„ฑ(๋ฌดํ–ฅ)

๋ฐฉํ–ฅ์ด ์—†๋Š” ์ •์ ์˜ ์Œ (u, v)์œผ๋กœ ์ง์„ ์œผ๋กœ ํ‘œํ˜„ํ•œ๋‹ค.

๋ฌด๋ฐฉํ–ฅ์„ฑ ๊ฐ„์„  (u, v)์™€ (v, u)๋Š” ๊ฐ™๋‹ค. (์–‘๋ฐฉํ–ฅ์„ ๊ฐ€๋ฆฌํ‚ด)

๋ฌด๋ฐฉํ–ฅ์„ฑ ๊ฐ„์„ ์„ ๊ฐ€์ง„ ๊ทธ๋ž˜ํ”„๋ฅผ ๋ฌด๋ฐฉํ–ฅ์„ฑ ๊ทธ๋ž˜ํ”„(Undirected Graph)๋ผ๊ณ  ํ•ฉ๋‹ˆ๋‹ค.

adjacent & incident

์ธ์ ‘ (adjacent)

๋ฌด๋ฐฉํ–ฅ์„ฑ ๊ทธ๋ž˜ํ”„์—์„œ ์ •์  u, v์— ๋Œ€ํ•˜์—ฌ ๊ฐ„์„ (u, v)์ด ์žˆ์œผ๋ฉด ์ •์  u๋Š” ์ •์  v์— ์ธ์ ‘(adjacent) ํ•˜๋‹ค๊ณ  ํ•œ๋‹ค. (์—ญ๋„ ์„ฑ๋ฆฝ)

๋ฐฉํ–ฅ์„ฑ ๊ทธ๋ž˜ํ”„์—์„œ ์ •์  u, v์— ๋Œ€ํ•˜์—ฌ ๊ฐ„์„ (u,v)์ด ์žˆ์œผ๋ฉด ์ •์  v๋Š” ์ •์  u์— ์ธ์ ‘ํ•œ๋‹ค๊ณ  ํ•œ๋‹ค. (์—ญ์€ ์„ฑ๋ฆฝํ•˜์ง€ ์•Š์Œ.)

๋ถ€์† (incident)

๋ฌด๋ฐฉํ–ฅ ๊ทธ๋ž˜ํ”„์—์„œ ์ •์  u,v์— ๋Œ€ํ•˜์—ฌ ๊ฐ„์„ (u, v)์ด ์žˆ์œผ๋ฉด ๊ฐ„์„ (u, v)์€ ์ •์  u์™€ v์— ๋ถ€์†(incident)ํ•œ๋‹ค๊ณ  ํ•ฉ๋‹ˆ๋‹ค.

Self-loop & isolated

self-loop

ํ•œ ๊ฐ„์„ ์ด ๊ฐ™์€ ์ •์ ์— ๋ถ€์†ํ•ด ์žˆ์„ ๋•Œ self-loop๋ผ๊ณ  ํ•ฉ๋‹ˆ๋‹ค. e = (u, u)

isolated

๊ฐ„์„ ์ด ์—†๋Š” ๊ฒฝ์šฐ๋ฅผ ๋งํ•˜๋ฉฐ ๊ฐ„์„ ์ด ์—†๋Š” ์ •์ ์„ isolated vertex๋ผ๊ณ  ํ•ฉ๋‹ˆ๋‹ค.

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