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28-xxubin04 #108

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Feb 19, 2024
Merged

28-xxubin04 #108

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33 changes: 33 additions & 0 deletions xxubin04/Binary Search/2805_나무 자르기.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
input = open(0).readline

tree_num, length = map(int, input().split())
trees = sorted(list(map(int, input().split())))

def binary_search(target, trees):
start = 0
end = trees[-1]

while start <= end:
mid = (start + end) // 2
cutted_trees = 0

for i in trees:
if (i - mid) >= 0:
cutted_trees += (i - mid)
Comment on lines +12 to +16
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채현이 PR에서도 설명한 부분이긴 한데,
이진 탐색 문제가 어려워질 수록 start, end 값을 조정하기 위한 조건 판별 코드가 길어집니다.
보통 이 부분은 check란 이름의 함수로 따로 분리하는 편입니다.

def check(cutter_height):
    sum_remain = 0
    for tree_height in trees:
        if tree_height > height_of_cutter:
            sum_remain += (tree_height - cutter_height)
            
    return sum_remain


if cutted_trees == target:
return mid
elif cutted_trees > target:
start = mid + 1
else:
end = mid - 1

if cutted_trees >= target:
ans = mid
else:
ans = mid - 1
Comment on lines +18 to +28
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위 check를 이용한다고 했을 때,

ans = 0
lo, hi = 1, max(trees)
while lo <= hi:
    mid = (lo + hi) // 2
    
    if check(mid) >= M:  # 자르고 남은 나무 길이 합이 원래 가져가고자 했던 길이보다 많거나 같으면
        ans = mid  # 현재 커팅 지점을 최대 지점으로 저장
        lo = mid + 1  # 하한선 증가
    else:  # 아니라면
        hi = mid - 1  # 상한선 감소
        
print(ans)

이런 식으로 조건을 더 간략하게 할 수 있겠죠?


return ans


print(binary_search(length, trees))
3 changes: 2 additions & 1 deletion xxubin04/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -28,4 +28,5 @@
| 24차시 | 2024.01.29 | DP | <a href="https://www.acmicpc.net/problem/1495">[1495]기타리스트</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/86 |
| 25차시 | 2024.02.01 | 구현 | <a href="https://leetcode.com/problems/roman-to-integer/">[13]Roman to Integer</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/91 |
| 26차시 | 2024.02.05 | 에라토스테네스의 체 | <a href="https://www.acmicpc.net/problem/4948">[4948]베르트랑 공준</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/94 |
| 27차시 | 2024.02.08 | 수학 | <a href="https://www.acmicpc.net/problem/2885">[2885]초콜릿 식사</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/98 |
| 27차시 | 2024.02.08 | 수학 | <a href="https://www.acmicpc.net/problem/2885">[2885]초콜릿 식사</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/98 |
| 28차시 | 2024.02.15 | 이진탐색 | <a href="https://www.acmicpc.net/problem/2805">[2805]나무 자르기</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-3/pull/108 |