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[daehyun99] WEEK02 solutions#2687

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[daehyun99] WEEK02 solutions#2687
daehyun99 wants to merge 4 commits into
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@daehyun99

@daehyun99 daehyun99 commented Jun 29, 2026

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๋‹ต์•ˆ ์ œ์ถœ ๋ฌธ์ œ

์ž‘์„ฑ์ž ์ฒดํฌ ๋ฆฌ์ŠคํŠธ

  • Projects์˜ ์˜ค๋ฅธ์ชฝ ๋ฒ„ํŠผ(โ–ผ)์„ ๋ˆŒ๋Ÿฌ ํ™•์žฅํ•œ ๋’ค, Week๋ฅผ ํ˜„์žฌ ์ฃผ์ฐจ๋กœ ์„ค์ •ํ•ด์ฃผ์„ธ์š”.
  • ๋ฌธ์ œ๋ฅผ ๋ชจ๋‘ ํ‘ธ์‹œ๋ฉด ํ”„๋กœ์ ํŠธ์—์„œ Status๋ฅผ In Review๋กœ ์„ค์ •ํ•ด์ฃผ์„ธ์š”.
  • ์ฝ”๋“œ ๊ฒ€ํ† ์ž 1๋ถ„ ์ด์ƒ์œผ๋กœ๋ถ€ํ„ฐ ์Šน์ธ์„ ๋ฐ›์œผ์…จ๋‹ค๋ฉด PR์„ ๋ณ‘ํ•ฉํ•ด์ฃผ์„ธ์š”.

๊ฒ€ํ† ์ž ์ฒดํฌ ๋ฆฌ์ŠคํŠธ

Important

๋ณธ์ธ ๋‹ต์•ˆ ์ œ์ถœ ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๋‹ค๋ฅธ ๋ถ„ PR ํ•˜๋‚˜ ์ด์ƒ์„ ๋ฐ˜๋“œ์‹œ ๊ฒ€ํ† ๋ฅผ ํ•ด์ฃผ์…”์•ผ ํ•ฉ๋‹ˆ๋‹ค!

  • ๋ฐ”๋กœ ์ด์ „์— ์˜ฌ๋ผ์˜จ PR์— ๋ณธ์ธ์„ ์ฝ”๋“œ ๋ฆฌ๋ทฐ์–ด๋กœ ์ถ”๊ฐ€ํ•ด์ฃผ์„ธ์š”.
  • ๋ณธ์ธ์ด ๊ฒ€ํ† ํ•ด์•ผํ•˜๋Š” PR์˜ ๋‹ต์•ˆ ์ฝ”๋“œ์— ํ”ผ๋“œ๋ฐฑ์„ ์ฃผ์„ธ์š”.
  • ํ† ์š”์ผ ์ „๊นŒ์ง€ PR์„ ๋ณ‘ํ•ฉํ•  ์ˆ˜ ์žˆ๋„๋ก ์Šน์ธํ•ด์ฃผ์„ธ์š”.

@dalestudy

dalestudy Bot commented Jun 29, 2026

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๐Ÿ“Š daehyun99 ๋‹˜์˜ ํ•™์Šต ํ˜„ํ™ฉ

์ด๋ฒˆ ์ฃผ ์ œ์ถœ ๋ฌธ์ œ

๋ฌธ์ œ ๋‚œ์ด๋„ ์œ ํ˜• ๋ถ„์„
3sum Medium โœ… ์˜๋„ํ•œ ์œ ํ˜•
climbing-stairs Easy โš ๏ธ ์œ ํ˜• ๋ถˆ์ผ์น˜
product-of-array-except-self Medium โš ๏ธ ์œ ํ˜• ๋ถˆ์ผ์น˜
valid-anagram Easy โœ… ์˜๋„ํ•œ ์œ ํ˜•
validate-binary-search-tree Medium โœ… ์˜๋„ํ•œ ์œ ํ˜•

๋ˆ„์  ํ•™์Šต ์š”์•ฝ

  • ํ’€์ดํ•œ ๋ฌธ์ œ: 5 / 75๊ฐœ
  • ์ด๋ฒˆ ์ฃผ ์œ ํ˜• ์ผ์น˜์œจ: 60% (5๋ฌธ์ œ ์ค‘ 3๋ฌธ์ œ ์ผ์น˜)

๋ฌธ์ œ ํ’€์ด ํ˜„ํ™ฉ

์นดํ…Œ๊ณ ๋ฆฌ ์ง„ํ–‰๋„ ์™„๋ฃŒ
Heap โ– โ– โ–กโ–กโ–กโ–กโ–ก 1 / 3 (Medium 1)
Array โ– โ–กโ–กโ–กโ–กโ–กโ–ก 2 / 10 (Easy 2)
Graph โ– โ–กโ–กโ–กโ–กโ–กโ–ก 1 / 8 (Medium 1)
Dynamic Programming โ– โ–กโ–กโ–กโ–กโ–กโ–ก 1 / 11 (Medium 1)
Binary โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 5 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ
Interval โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 5 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ
Linked List โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 6 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ
Matrix โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 4 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ
String โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 10 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ
Tree โ–กโ–กโ–กโ–กโ–กโ–กโ–ก 0 / 14 โ† ์•„์ง ์‹œ์ž‘ ์•ˆ ํ•จ

๐Ÿค– ์ด ๋Œ“๊ธ€์€ GitHub App์„ ํ†ตํ•ด ์ž๋™์œผ๋กœ ์ž‘์„ฑ๋˜์—ˆ์Šต๋‹ˆ๋‹ค.

๐Ÿ”ข API ์‚ฌ์šฉ๋Ÿ‰ (gpt-5-nano)
์š”์ฒญ ์ž…๋ ฅ ํ† ํฐ ์ถœ๋ ฅ ํ† ํฐ ํ•ฉ๊ณ„ ๋น„์šฉ
1 300 44 344 $0.000033
2 640 107 747 $0.000075
3 989 140 1,129 $0.000105
4 1,909 230 2,139 $0.000187
ํ•ฉ๊ณ„ 3,838 521 4,359 $0.000400

@jthw1005 jthw1005 self-requested a review June 29, 2026 19:41

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collections ์˜ Counter๊ฐ€ ๊ธฐ๋ณธ์ ์œผ๋กœ defaultdict(int) ์ฒ˜๋Ÿผ ์—†๋Š” ํ‚ค๊ฐ’์— ๋Œ€ํ•ด 0์„ ๋ณด๋‚ธ๋‹ค๋Š”๊ฒƒ์„ ์•Œ๊ณ  ๊ณ„์‹ค๊นŒ์š”?
๊ทธ๊ฑธ ์“ฐ์‹œ๋ฉด ํ›จ์”ฌ ๊ฐ„๋‹จํ•˜๊ฒŒ ์ž‘์„ฑํ•˜์‹ค์ˆ˜ ์žˆ์œผ์‹ค๊ฑฐ์—์š”!

Comment thread 3sum/daehyun99.py

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Two Pointers, Sorting
  • ์„ค๋ช…: ์ฃผ ์ฝ”๋“œ์˜ ํ•ต์‹ฌ์€ ์ด์ค‘ ํฌ์ธํ„ฐ(l, r)๋ฅผ ์ด์šฉํ•ด ์ •๋ ฌ๋œ ๋ฐฐ์—ด์—์„œ ํ•ฉ์ด 0์ด ๋˜๋„๋ก ์ฐพ๋Š” ๊ตฌ์กฐ๋กœ, ์ค‘๋ณต ์ œ๊ฑฐ๋ฅผ ์œ„ํ•ด ํฌ์ธํ„ฐ ์ด๋™ ์‹œ๊ฑด์„ ์‚ฌ์šฉํ•œ๋‹ค. ์ด๋Š” Two Pointers ํŒจํ„ด์˜ ๋Œ€ํ‘œ์  ์˜ˆ์ด๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n^2)
Space O(1)

ํ”ผ๋“œ๋ฐฑ: ์ •๋ ฌ๊ณผ ๋‘ ํฌ์ธํ„ฐ๋กœ ์ค‘๋ณต์„ ๊ฑด๋„ˆ๋›ฐ๋Š” ๋ฐฉ์‹์œผ๋กœ ํ•„์š”ํ•˜์ง€ ์•Š์€ ํƒ์ƒ‰์„ ์ œ๊ฑฐํ–ˆ๋‹ค. ๋‹จ์ผ ๋ฃจํ”„ ๋‚ด์—์„œ ์ขŒ์šฐ ํฌ์ธํ„ฐ๋ฅผ ์กฐ์ •ํ•˜๋ฏ€๋กœ ์‹œ๊ฐ„ ๋ณต์žก๋„๋Š” ์ด ๋ฌธ์ œ์˜ ์ตœ์ ์— ๊ฐ€๊น๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ํ˜„์žฌ ๊ตฌํ˜„์ด ์ ์ ˆํ•ด ๋ณด์ž…๋‹ˆ๋‹ค.

๐Ÿ’ก ํ’€์ด์— ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ฃผ์„์œผ๋กœ ๋‚จ๊ฒจ๋ณด์„ธ์š”!

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Dynamic Programming, Greedy
  • ์„ค๋ช…: ์ฃผ์–ด์ง„ ์ฝ”๋“œ๋Š” ํ”ผ๋ณด๋‚˜์น˜ ํ˜•ํƒœ์˜ ๊ณ„๋‹จ ์˜ค๋ฅด๊ธฐ ๋ฌธ์ œ๋ฅผ ๋‹ค์–‘ํ•œ ์กฐํ•ฉ์œผ๋กœ ์„ธ๋Š” ๋ฐฉ์‹์œผ๋กœ ๊ตฌํ˜„๋˜๋ฉฐ, DP์˜ ๊ธฐ๋ณธ ์•„์ด๋””์–ด(๋ถ€๋ถ„ ๋ฌธ์ œ์˜ ํ•ฉ)์™€ ํƒ์ƒ‰์  ์ ‘๊ทผ(๊ทธ๋ฆฌ๋””ํ˜•์œผ๋กœ ํŠน์ • ๋‹จ๊ณ„์˜ ์„ ํƒ ๋ถ„๊ธฐ)์„ ํ†ตํ•ด ํ•ด๋ฅผ ๊ตฌํ•œ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n)
Space O(1)

ํ”ผ๋“œ๋ฐฑ: ๊ฐ ๋‹จ๊ณ„์˜ ๊ฒฝ์šฐ์˜ ์ˆ˜๋ฅผ ์ƒํƒœ๋กœ ์œ ์ง€ํ•ด ๋น ๋ฅด๊ฒŒ ๋ˆ„์ ํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ๊ตฌํ˜„๋˜์—ˆ์œผ๋‚˜, ํ˜„์žฌ ๊ตฌํ˜„์€ ์ง๊ด€์ ์ด์ง€ ์•Š์„ ์ˆ˜ ์žˆ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ์†๋„์™€ ๊ฐ€๋…์„ฑ์„ ์œ„ํ•ด ๊ฐ„๋‹จํ•œ ํ”ผ๋ณด๋‚˜์น˜ DP๋กœ ๊ตฌํ˜„ํ•˜๊ฑฐ๋‚˜, ๊ณต๊ฐ„์„ ๋” ์ ˆ์•ฝํ•˜๋Š” ํ˜•ํƒœ๋กœ ๊ฐœ์„ ํ•ด ๋ณด์„ธ์š”.

๐Ÿ’ก ํ’€์ด์— ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ฃผ์„์œผ๋กœ ๋‚จ๊ฒจ๋ณด์„ธ์š”!

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Prefix/Suffix Product (a.k.a. product of array except self) pattern cannot be generic name, Hash Map / Hash Set, Division and Edge Case Handling
  • ์„ค๋ช…: ๋ฐฐ์—ด ์ „์ฒด ๊ณฑ์„ ํ•œ ๋ฒˆ์— ๊ตฌํ•œ ๋’ค ๊ฐ ์›์†Œ๋ฅผ ๋‚˜๋ˆ„๋Š” ๋ฐฉ์‹๊ณผ 0์˜ ์œ„์น˜๋ฅผ ๊ด€๋ฆฌํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•œ๋‹ค. 0์˜ ๊ฐœ์ˆ˜์— ๋”ฐ๋ผ ๊ฒฐ๊ณผ๋ฅผ ๋‹ค๋ฅด๊ฒŒ ๋ฐ˜ํ™˜ํ•˜๋Š” ๋กœ์ง์€ ์˜ˆ์™ธ ์ฒ˜๋ฆฌ ํŒจํ„ด์— ํ•ด๋‹นํ•œ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n)
Space O(1)

ํ”ผ๋“œ๋ฐฑ: ์ œ๋กœ ์ฒ˜๋ฆฌ๋ฅผ ๋ช…ํ™•ํ•˜๊ฒŒ ๋ถ„๋ฆฌํ–ˆ๊ณ , ์ถ”๊ฐ€ ๋ฐฐ์—ด ์—†์ด๋„ ๊ฒฐ๊ณผ๋ฅผ ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋Š” ๊ตฌ์กฐ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ํŠนํžˆ ์ œ๋กœ๊ฐ€ ํ•˜๋‚˜์ธ ๊ฒฝ์šฐ์™€ ์—†์„ ๋•Œ์˜ ๋ถ„๊ธฐ ๋กœ์ง์„ ๊ฐ„๊ฒฐํ•˜๊ฒŒ ๋‹ค๋“ฌ์œผ๋ฉด ๊ฐ€๋…์„ฑ์ด ํ–ฅ์ƒ๋  ์ˆ˜ ์žˆ๋‹ค.

๐Ÿ’ก ํ’€์ด์— ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ฃผ์„์œผ๋กœ ๋‚จ๊ฒจ๋ณด์„ธ์š”!

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Hash Map / Hash Set, Two Pointers, Greedy
  • ์„ค๋ช…: ๋‘ ๋ฌธ์ž์—ด์˜ ๋ฌธ์ž ๋นˆ๋„๋ฅผ ํ•ด์‹œ๋งต์œผ๋กœ ํ•ฉ ๋น„๊ตํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ๋™์ž‘ํ•˜๋ฉฐ, ์„œ๋กœ ๋‹ค๋ฅธ ๋ฌธ์ž์˜ ๊ฐœ์ˆ˜๋ฅผ ๋น ๋ฅด๊ฒŒ ํ™•์ธํ•ด ํ›„๋ณด๋ฅผ ์ œ๊ฑฐํ•ฉ๋‹ˆ๋‹ค. ๋‘ ํฌ์ธํ„ฐ์ฒ˜๋Ÿผ zip์œผ๋กœ ํ•œ ๊ธ€์ž์”ฉ ์ง์„ ๋งž์ถ”๋Š” ๋А๋‚Œ๋„ ์žˆ์Šต๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n)
Space O(k)

ํ”ผ๋“œ๋ฐฑ: ์นด์šดํŠธ ์ฐจ์ด๋ฅผ ์ด์šฉํ•ด ํ•œ ๋ฒˆ์˜ ์ˆœํšŒ๋กœ ๊ฒฐ๊ณผ๋ฅผ ํŒ์ •ํ•œ๋‹ค. ๊ฐ„๋‹จํ•˜๊ณ  ๋น ๋ฅธ ๋ฐฉ๋ฒ•์ด๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ํ•„์š” ์—†์„ ๋•Œ๋Š” defaultdict ์‚ฌ์šฉ ๋Œ€์‹  ๋ฐฐ์—ด ์ธ๋ฑ์Šค ๊ธฐ๋ฐ˜ ์นด์šดํŠธ๋กœ ๋” ๋น ๋ฅด๊ฒŒ ๊ตฌํ˜„ ๊ฐ€๋Šฅ.

๐Ÿ’ก ํ’€์ด์— ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ฃผ์„์œผ๋กœ ๋‚จ๊ฒจ๋ณด์„ธ์š”!

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Binary Search, Depth-First Search
  • ์„ค๋ช…: BST ๊ฒ€์ฆ ๋ฌธ์ œ์—์„œ ํŠธ๋ฆฌ๋ฅผ ์žฌ๊ท€์ ์œผ๋กœ ์ˆœํšŒํ•˜๋ฉฐ ๊ฐ ๋…ธ๋“œ์˜ ๊ฐ’์ด ์™ผ์ชฝ/์˜ค๋ฅธ์ชฝ ์„œ๋ธŒํŠธ๋ฆฌ์˜ ๋ฒ”์œ„ ์ œ์•ฝ์„ ๋งŒ์กฑํ•˜๋Š”์ง€ ํ™•์ธํ•œ๋‹ค. ์žฌ๊ท€์  ํƒ์ƒ‰(DFS)์œผ๋กœ ์ž์‹ ๋…ธ๋“œ์˜ ํ—ˆ์šฉ ๋ฒ”์œ„๋ฅผ ์ขํ˜€ ๊ฐ€๋Š” ๋ฐฉ์‹์ด๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n)
Space O(h)

ํ”ผ๋“œ๋ฐฑ: ์ขŒ์šฐ ์ž์‹ ๋…ธ๋“œ์— ๋Œ€ํ•ด ์ƒํ•œ/ํ•˜ํ•œ ๊ฐ’์„ ์ „๋‹ฌํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ์ค‘๋ณต ํฌํ•จ ์—ฌ๋ถ€๋ฅผ ์˜ฌ๋ฐ”๋ฅด๊ฒŒ ํŒ๋‹จํ•œ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ์Šคํƒ์„ ์ด์šฉํ•œ ๋น„์žฌ๊ท€ ๊ตฌํ˜„์œผ๋กœ ์žฌ๊ท€ ๊นŠ์ด๋ฅผ ์ œ์–ดํ•  ์ˆ˜ ์žˆ๋‹ค.

๐Ÿ’ก ํ’€์ด์— ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ฃผ์„์œผ๋กœ ๋‚จ๊ฒจ๋ณด์„ธ์š”!

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