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[dahyeong-yun] WEEK 02 solutions#2684

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[dahyeong-yun] WEEK 02 solutions#2684
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@dahyeong-yun

@dahyeong-yun dahyeong-yun 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 dahyeong-yun ๋‹˜์˜ ํ•™์Šต ํ˜„ํ™ฉ

์ด๋ฒˆ ์ฃผ ์ œ์ถœ ๋ฌธ์ œ

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

๋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
1 577 67 644 $0.000056
2 577 37 614 $0.000044
3 3,438 198 3,636 $0.000251
4 3,437 185 3,622 $0.000246
5 3,435 223 3,658 $0.000261
ํ•ฉ๊ณ„ 11,464 710 12,174 $0.000857

Comment thread 3sum/dahyeong-yun.java

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Two Pointers, Sorting
  • ์„ค๋ช…: 3Sum์€ ์ •๋ ฌ ํ›„ ๊ณ ์ • ๊ฐ’์— ๋Œ€ํ•ด ์ขŒ์šฐ ํฌ์ธํ„ฐ๋ฅผ ์ด๋™์‹œํ‚ค๋Š” ํˆฌ ํฌ์ธํ„ฐ ๊ธฐ๋ฒ•์œผ๋กœ ์ค‘๋ณต ์ œ๊ฑฐ๋ฅผ ์ˆ˜ํ–‰ํ•ฉ๋‹ˆ๋‹ค. ์‹œ๊ฐ„๋ณต์žก๋„๋Š” O(n^2)์ด๋ฉฐ, ์ถ”๊ฐ€ ๊ณต๊ฐ„์€ ์ƒ์ˆ˜์— ๊ฐ€๊น์Šต๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

๋ณต์žก๋„
Time O(n^2)
Space O(1)

ํ”ผ๋“œ๋ฐฑ: ์ •๋ ฌ์œผ๋กœ ์ค‘๋ณต์„ ์ œ๊ฑฐํ•˜๊ณ  ํˆฌ ํฌ์ธํ„ฐ๋กœ ์กฐํ•ฉ์„ ์ฐพ๋Š” ์ „ํ˜•์ ์ธ 3Sum ํ•ด๋ฒ•์ž…๋‹ˆ๋‹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
  • ์„ค๋ช…: ํ”ผ๋ณด๋‚˜์น˜ ํ˜•ํƒœ๋กœ ๊ฐ ๋‹จ๊ณ„์˜ ๊ฒฝ์šฐ์˜ ์ˆ˜๋ฅผ ์ด์ „ ์ƒํƒœ๋“ค๋กœ๋ถ€ํ„ฐ ํ•ฉ์‚ฐํ•˜๋Š” DP ๊ธฐ๋ฒ•์„ ์‚ฌ์šฉํ•ฉ๋‹ˆ๋‹ค. ์ ํ™”์‹์œผ๋กœ ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•˜๊ณ , ๋ฐฐ์—ด์„ ์‚ฌ์šฉํ•ด ๋ถ€๋ถ„ํ•ด๋ฅผ ์ €์žฅํ•˜๋‚˜ ์ตœ์ ํ™” ๊ฐ€๋Šฅ์„ฑ๋„ ์ดํ•ดํ•  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

์œ ์ € ๋ถ„์„ ์‹ค์ œ ๋ถ„์„ ๊ฒฐ๊ณผ
Time O(n) O(n) โœ…
Space O(n) O(n) โœ…

ํ”ผ๋“œ๋ฐฑ: ์ „ํ˜•์ ์ธ DP ํ’€์ด๋กœ ๊ฐ ๋‹จ๊ณ„ ์ด์ „ ๋‘ ๋‹จ๊ณ„์˜ ํ•ฉ์œผ๋กœ ํ˜„์žฌ ๊ฒฝ์šฐ์˜ ์ˆ˜๋ฅผ ๊ตฌํ•ฉ๋‹ˆ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ๋งŒ์•ฝ ๊ณต๊ฐ„์„ ๋” ์ ˆ์•ฝํ•˜๊ณ  ์‹ถ๋‹ค๋ฉด two-variable๋กœ๋งŒ ํ•ด๊ฒฐํ•˜๋Š” ์ตœ์ ํ™”๋„ ๊ฐ€๋Šฅํ•ฉ๋‹ˆ๋‹ค.

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Two Pointers, Dynamic Programming, Hash Map / Hash Set
  • ์„ค๋ช…: ํ•ด๋‹น ์ฝ”๋“œ๋Š” ๋‘ ๋ฐฐ์—ด(ํ”„๋ฆฌํ”ฝ์Šค/์„œํ”ฝ์Šค) ๊ฐœ๋…์œผ๋กœ ํ•œ ๋ฐฐ์—ด์„ ๋‘ ๋ฒˆ ์ˆœํšŒํ•˜๋ฉฐ ๊ณฑ์„ ๋ˆ„์  ๊ณ„์‚ฐํ•˜๋Š” ๋ฐฉ์‹์ด๋‹ค. ๋‘ ํฌ์ธํ„ฐ ์œ ์‚ฌํ•œ ์ง„ํ–‰ ํ˜•ํƒœ๋กœ ์™ผ์ชฝ/์˜ค๋ฅธ์ชฝ ๋ˆ„์  ๊ณฑ์„ ์ด์šฉํ•ด ๊ฒฐ๊ณผ๋ฅผ ๊ตฌํ•˜๋Š” ํŒจํ„ด๊ณผ ๋ถ€๋ถ„ ๋ฌธ์ œ์˜ ๊ณฑ์„ ๊ณฑ์…ˆ์œผ๋กœ ํ•ฉ์„ฑํ•˜๋Š” ์•„์ด๋””์–ด๊ฐ€ ์ ์šฉ๋œ๋‹ค. ๋˜ํ•œ ์ตœ์ ํ™”๋œ ๊ณต๊ฐ„ ๋ณต์žก๋„ ๋‹ฌ์„ฑ์„ ์œ„ํ•œ DP์  ๋ˆ„์  ๊ฒฐ๊ณผ ์ €์žฅ ํ˜•ํƒœ๊ฐ€ ๋ณด์ธ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

์œ ์ € ๋ถ„์„ ์‹ค์ œ ๋ถ„์„ ๊ฒฐ๊ณผ
Time O(n) O(n) โœ…
Space O(n) O(1) โŒ

ํ”ผ๋“œ๋ฐฑ: ๊ณต๊ฐ„์„ ์ค„์ด๋ฉด์„œ ๋ชจ๋“  ์›์†Œ์˜ ๊ณฑ์„ ๊ตฌํ•˜๋Š” ํ‘œ์ค€ ์†”๋ฃจ์…˜์ด๋ฉฐ ๋‘ ํŒจ์Šค ๋ฐฉ์‹์ด ํšจ๊ณผ์ ์ž…๋‹ˆ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ๊ฐ„๋‹จํ•œ ๊ตฌํ˜„์ด์ง€๋งŒ ๋ณ€์ˆ˜ ๋ช…์„ ๋” ์ง๊ด€์ ์œผ๋กœ ๋ฐ”๊ฟ” ๊ฐ€๋…์„ฑ์„ ๋†’์ผ ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Binary Search, Hash Map / Hash Set, Greedy, Divide and Conquer, Dynamic Programming, Two Pointers, Sliding Window, Fast & Slow Pointers, BFS, DFS, Backtracking, Union Find, Trie, Bit Manipulation, Heap / Priority Queue, Monotonic Stack
  • ์„ค๋ช…: ์ฃผ์–ด์ง„ ์ •๋ ฌ ๊ธฐ๋ฐ˜ ๋น„๊ต๋กœ ์• ๋„ˆ๊ทธ๋žจ ์—ฌ๋ถ€๋ฅผ ํŒ๋‹จํ•˜๋Š”๋ฐ, ๋ฌธ์ž์—ด์„ ๋ฌธ์ž ๋ฐฐ์—ด๋กœ ๋ณ€ํ™˜ ํ›„ ์ •๋ ฌํ•˜๊ณ  ๋น„๊ตํ•œ๋‹ค. ์ •๋ ฌ์ด ํ•ต์‹ฌ ์—ฐ์‚ฐ์ด๋ฉฐ, ์‹œ๊ฐ„ ๋ณต์žก๋„๋Š” O(n log n)์ด๊ณ  ์ถ”๊ฐ€ ๊ณต๊ฐ„์€ O(n)์ด๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

์œ ์ € ๋ถ„์„ ์‹ค์ œ ๋ถ„์„ ๊ฒฐ๊ณผ
Time O(n log n) O(n log n) โœ…
Space O(n) O(n) โœ…

ํ”ผ๋“œ๋ฐฑ: ๋ฌธ์ž์—ด ๊ธธ์ด๊ฐ€ ์ปค๋„ ๋น„๊ต์  ๋‹จ์ˆœํ•˜๊ฒŒ ๊ตฌํ˜„๋œ ํ•ด๋ฒ•์ž…๋‹ˆ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: ์ถ”๊ฐ€ ์ตœ์ ํ™”๋ฅผ ์›ํ•˜๋ฉด ๋ฌธ์ž ๋นˆ๋„ ์นด์šดํŠธ๋ฅผ ์ด์šฉํ•œ O(n) ํ’€์ด๋„ ๊ณ ๋ คํ•ด๋ณผ ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Hash Map / Hash Set, Sorting
  • ์„ค๋ช…: ์ฃผ์–ด์ง„ ํ’€์ด์—์„œ ๋‘ ๋ฌธ์ž์—ด์˜ ์• ๋‹ˆ๊ทธ๋žจ ์—ฌ๋ถ€๋ฅผ ํŒ๋‹จํ•˜๊ธฐ ์œ„ํ•ด ๋ฌธ์ž๋ฅผ ๋ฐฐ์—ด๋กœ ๋งŒ๋“ค๊ณ  ์ •๋ ฌํ•œ ๋’ค ๋น„๊ตํ•ฉ๋‹ˆ๋‹ค. ์ •๋ ฌ์€ n log n ์‹œ๊ฐ„, ์ถ”๊ฐ€ ๊ณต๊ฐ„์€ ๋ฐฐ์—ด ๋ณต์ œ์— ์˜ํ•ด O(n)๋กœ ํ•„์š”ํ•˜๋ฏ€๋กœ ํŒจํ„ด์€ ํ•ด์‹œ ๋งต/์„ธํŠธ๋ณด๋‹จ ์ •๋ ฌ ๊ธฐ๋ฐ˜ ์ ‘๊ทผ์— ํ•ด๋‹นํ•ฉ๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

์œ ์ € ๋ถ„์„ ์‹ค์ œ ๋ถ„์„ ๊ฒฐ๊ณผ
Time O(n log n) O(n log n) โœ…
Space O(n) O(n) โœ…

ํ”ผ๋“œ๋ฐฑ: ํ˜„์žฌ ์ฝ”๋“œ๊ฐ€ ์ž˜๋ชป๋œ ๋ฌธ์ œ ์„ค๋ช…๊ณผ ํ•จ๊ป˜ ๊ฐ™์€ ์• ๋„ˆ๊ทธ๋žจ ์ฝ”๋“œ๋ฅผ ๋ฐ˜๋ณตํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. BST ๊ฒ€์‚ฌ ๊ตฌํ˜„์ด ํ•„์š”ํ•ฉ๋‹ˆ๋‹ค.

๊ฐœ์„  ์ œ์•ˆ: BST ๊ฒ€์‚ฌ๋ฅผ ์˜ฌ๋ฐ”๋ฅด๊ฒŒ ๊ตฌํ˜„ํ•˜๊ณ , ์ค‘๋ณต ์ œ๊ฑฐ์™€ ๊ฒฝ๊ณ„ ์กฐ๊ฑด์„ ์‹ ๊ฒฝ ์จ์„œ ์ž‘์„ฑํ•ด ๋ณด์„ธ์š”.

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