(二分枚举) $O(nlog(n))$

二分枚举满足条件的E取最小值

python3 代码

def isValid(e, H):
    for h in H:
        if h > e:
            e -= h - e
        else:
            e += e - h
        if e < 0:
            return False
    return True

N = int(input())
H = [int(i) for i in input().split()]
l, r, mid = 0, 100000, 0
while l <= r:
    mid = (l + r) // 2
    if isValid(mid, H):
        r = mid - 1
    else:
        l = mid + 1
print(l)