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[dolphinflow86] WEEK 03 Solutions#2710

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@dolphinflow86

@dolphinflow86 dolphinflow86 commented Jul 5, 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 Jul 5, 2026

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๐Ÿ“Š dolphinflow86 ๋‹˜์˜ ํ•™์Šต ํ˜„ํ™ฉ

์ด๋ฒˆ ์ฃผ ์ œ์ถœ ๋ฌธ์ œ

๋ฌธ์ œ ๋‚œ์ด๋„ ์œ ํ˜• ๋ถ„์„
combination-sum Medium โœ… ์˜๋„ํ•œ ์œ ํ˜•
decode-ways Medium โœ… ์˜๋„ํ•œ ์œ ํ˜•
number-of-1-bits Easy โš ๏ธ ์œ ํ˜• ๋ถˆ์ผ์น˜
valid-palindrome Easy โœ… ์˜๋„ํ•œ ์œ ํ˜•

๋ˆ„์  ํ•™์Šต ์š”์•ฝ

  • ํ’€์ดํ•œ ๋ฌธ์ œ: 10 / 75๊ฐœ
  • ์ด๋ฒˆ ์ฃผ ์œ ํ˜• ์ผ์น˜์œจ: 75% (4๋ฌธ์ œ ์ค‘ 3๋ฌธ์ œ ์ผ์น˜)

๋ฌธ์ œ ํ’€์ด ํ˜„ํ™ฉ

์นดํ…Œ๊ณ ๋ฆฌ ์ง„ํ–‰๋„ ์™„๋ฃŒ
Array โ– โ– โ– โ–กโ–กโ–กโ–ก 4 / 10 (Medium 2, Easy 2)
Heap โ– โ– โ–กโ–กโ–กโ–กโ–ก 1 / 3 (Medium 1)
Dynamic Programming โ– โ–กโ–กโ–กโ–กโ–กโ–ก 2 / 11 (Easy 1, Medium 1)
Graph โ– โ–กโ–กโ–กโ–กโ–กโ–ก 1 / 8 (Medium 1)
String โ– โ–กโ–กโ–กโ–กโ–กโ–ก 1 / 10 (Easy 1)
Tree โ– โ–กโ–กโ–กโ–กโ–กโ–ก 1 / 14 (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

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
1 517 37 554 $0.000041
2 312 77 389 $0.000046
3 1,205 129 1,334 $0.000112
4 1,271 129 1,400 $0.000115
5 1,766 156 1,922 $0.000151
ํ•ฉ๊ณ„ 5,071 528 5,599 $0.000465

@github-actions github-actions Bot added the py label Jul 5, 2026
@okyungjin okyungjin self-requested a review July 5, 2026 07:22

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@DaleStudy/coach ์ฃผ์„์— ๋ณต์žก๋„ ์ถ”๊ฐ€ ์™„๋ฃŒ

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Backtracking, Greedy
  • ์„ค๋ช…: ๊ฐ€๋Šฅํ•œ ๋ชจ๋“  ์กฐํ•ฉ์„ ํƒ์ƒ‰ํ•˜์—ฌ ๋ชฉํ‘œ๋ฅผ ๋งŒ์กฑํ•˜๋Š” ๊ฒฝ์šฐ๋ฅผ ์ฐพ๋Š” ๋ฐฉ์‹์œผ๋กœ backtracking์ด ์ฃผ ํŒจํ„ด์ž…๋‹ˆ๋‹ค. ์ฃผ์–ด์ง„ ์ฝ”๋“œ์—์„œ ํ›„๋ณด๋ฅผ ์ •๋ ฌํ•˜๊ณ  ๋‚จ์€ ํ•ฉ์ด 0์ด ๋  ๋•Œ๊นŒ์ง€ ์žฌ๊ท€์ ์œผ๋กœ ์กฐํ•ฉ์„ ํ™•์žฅํ•˜๋Š” ๊ตฌ์กฐ๊ฐ€ ๋Œ€ํ‘œ์ ์ด๋ฉฐ, ๊ฐ ์„ ํƒ์„ ๋˜๋Œ๋ ค ๋‹ค์Œ ํ›„๋ณด๋กœ ์‹œ๋„ํ•ฉ๋‹ˆ๋‹ค. ์ถ”๊ฐ€๋กœ ๋‚จ์€ ํ•ฉ์˜ ์กฐ๊ฑด์œผ๋กœ ๊ฐ€์ง€๋ฅผ ์ž๋ฅด๋Š” ๋ถ€๋ถ„์€ ํƒ์ƒ‰ ๊ณต๊ฐ„์„ ์ค„์ด๋Š” ํ˜•ํƒœ๋กœ ๊ทธ๋ฆฌ๋”” ์š”์†Œ๋ฅผ ์•”์‹œํ•ฉ๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

์œ ์ € ๋ถ„์„ ์‹ค์ œ ๋ถ„์„ ๊ฒฐ๊ณผ
Time O(N^(T/M)) O(K * N^K) โŒ
Space O(T/M) O(K) โŒ

ํ”ผ๋“œ๋ฐฑ: ์ •๋ ฌ๋œ ํ›„๋ณด ๋ฐฐ์—ด์— ๋Œ€ํ•ด start_index๋ถ€ํ„ฐ ๋ฐ˜๋ณตํ•˜๋ฉฐ ๋‚จ์€ ํ•ฉ์ด ํ›„๋ณด๋ฅผ ์ดˆ๊ณผํ•˜๋ฉด ๊ฐ€์ง€์น˜๊ธฐ๋ฅผ ํ•œ๋‹ค. ์žฌ๊ท€๋ฅผ ํ†ตํ•ด ๊ฐ ๊ฒฝ๋กœ๋ฅผ ์ถ”์ ํ•œ๋‹ค.

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

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Dynamic Programming, Memoization, Divide and Conquer
  • ์„ค๋ช…: ์ฃผ์–ด์ง„ ์ฝ”๋“œ๋Š” ๋ฌธ์ž์—ด์˜ ๋ถ€๋ถ„๋ฌธ์ œํ•ด๋ฅผ ์žฌ๊ท€์ ์œผ๋กœ ๋‚˜๋ˆ„๊ณ  ๋ฉ”๋ชจ์ด์ œ์ด์…˜์œผ๋กœ ์ค‘๋ณต ๊ณ„์‚ฐ์„ ์ œ๊ฑฐํ•˜๋Š” ํ˜•ํƒœ๋กœ, ์ƒํ–ฅ์‹์ด ์•„๋‹ˆ๋ผ ํƒ‘๋‹ค์šด DP(TOP-DOWN DP)์™€ ๋ฉ”๋ชจ์ด์ œ์ด์…˜ ํŒจํ„ด์ด ํ•ต์‹ฌ์ด๋‹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: ๋ฉ”๋ชจ์ด์ œ์ด์…˜์œผ๋กœ ์ค‘๋ณต ๊ณ„์‚ฐ์„ ํ”ผํ•˜๊ณ , 0 ์ฒ˜๋ฆฌ์™€ 10~26์˜ ๋‘ ์ž๋ฆฌ ๋ฒ”์œ„๋ฅผ ํ™•์ธํ•œ๋‹ค.

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

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Bit Manipulation
  • ์„ค๋ช…: ์ฃผ์–ด์ง„ ์ฝ”๋“œ๋Š” ์ด์ง„์ˆ˜์˜ ๊ฐ ์ž๋ฆฌ์ˆ˜๋ฅผ 2๋กœ ๋‚˜๋ˆ  ๋‚˜๋จธ์ง€๋ฅผ ํ™•์ธํ•˜๋ฉฐ 1์˜ ๋น„ํŠธ๋ฅผ ์„ธ๋Š” ๋ฐฉ์‹์œผ๋กœ ๋™์ž‘ํ•œ๋‹ค. ๋น„ํŠธ ๋ ˆ๋ฒจ ์—ฐ์‚ฐ์˜ ํ•œ ์˜ˆ๋กœ ๋น„ํŠธ ์ˆ˜๋ฅผ ๊ตฌํ•˜๋Š” ๊ณผ์ •์ด ํ•ต์‹ฌ์ด๋ฉฐ, ๋น„ํŠธ ์กฐ์ž‘์˜ ๊ธฐ๋ณธ ํŒจํ„ด์— ํ•ด๋‹นํ•œ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

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

ํ”ผ๋“œ๋ฐฑ: ๋น„ํŠธ ์นด์šดํŠธ์˜ ์ผ๋ฐ˜์  ๋ฐฉ๋ฒ•๊ณผ ๋‹ฌ๋ฆฌ ๋‚˜๋ˆ—์…ˆ/๋‚˜๋ˆ—์…ˆ์œผ๋กœ ๋ฐ˜๋ณตํ•˜๋ฏ€๋กœ ๋น„ํšจ์œจ์ ์ผ ์ˆ˜ ์žˆ๋‹ค. ๋น„ํŠธ ์—ฐ์‚ฐ์œผ๋กœ ๊ฐœ์„  ๊ฐ€๋Šฅ.

๊ฐœ์„  ์ œ์•ˆ: ๊ณ ๋ คํ•ด๋ณผ ๋งŒํ•œ ๋Œ€์•ˆ: n & (n - 1) ์—ฐ์‚ฐ์œผ๋กœ 1 ๋น„ํŠธ์”ฉ ์ œ๊ฑฐํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ์‹œ๊ฐ„ ๋ณต์žก๋„๋ฅผ ์ตœ์ ํ™”

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๐Ÿท๏ธ ์•Œ๊ณ ๋ฆฌ์ฆ˜ ํŒจํ„ด ๋ถ„์„

  • ํŒจํ„ด: Two Pointers
  • ์„ค๋ช…: ๋‘ ๊ฐ€์ง€ ๊ตฌํ˜„ ๋ชจ๋‘ ๋ฌธ์ž์—ด์„ ์•ž๋’ค์—์„œ ๋น„๊ตํ•˜๋ฉฐ ํฌ์ธํ„ฐ๋ฅผ ์›€์ง์ด๋Š” ๊ตฌ์กฐ๋กœ, ๋ถ€๋ถ„ ๋ฌธ์ž์—ด ์ถ”์ถœ ์—†์ด ์‹ค์‹œ๊ฐ„์œผ๋กœ ๋Œ€์กฐํ•˜๊ฑฐ๋‚˜(1๋ฒˆ) ์ƒˆ๋กœ์šด ๋ฌธ์ž์—ด๋กœ ๋งŒ๋“  ๋’ค ์–‘์ชฝ์—์„œ ๋น„๊ตํ•˜๋Š”(2๋ฒˆ) ๋ฐฉ์‹์œผ๋กœ ํŒ”๋ฆฐ๋“œ๋กฌ์„ ํ™•์ธํ•ฉ๋‹ˆ๋‹ค.

๐Ÿ“Š ์‹œ๊ฐ„/๊ณต๊ฐ„ ๋ณต์žก๋„ ๋ถ„์„

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

ํ”ผ๋“œ๋ฐฑ: ํ•„์ˆ˜ ์กฐ๊ฑด์ธ ๋น„์•ŒํŒŒ๋„˜ ๋ฌธ์ž ๊ฑด๋„ˆ๋›ฐ๊ธฐ์™€ ๋Œ€์†Œ๋ฌธ์ž ๋น„๊ต๋ฅผ ์ ์ ˆํžˆ ์ฒ˜๋ฆฌํ•œ๋‹ค.

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

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