Python 为什么我要找到最长的递增子序列而不是最长的递减子序列?
我试图在Onlogn中查找数组中最长的递减子序列。不确定这是否真的需要Onlogn,但无论如何,这将返回最长递增子序列的长度,而不是最长递减子序列的长度。有人能帮忙吗Python 为什么我要找到最长的递增子序列而不是最长的递减子序列?,python,algorithm,subsequence,Python,Algorithm,Subsequence,我试图在Onlogn中查找数组中最长的递减子序列。不确定这是否真的需要Onlogn,但无论如何,这将返回最长递增子序列的长度,而不是最长递减子序列的长度。有人能帮忙吗 def binary_search(L, l, r, key): while (r - l > 1): m = l + (r - l)//2 if (L[m] >= key): r = m else: l
def binary_search(L, l, r, key):
while (r - l > 1):
m = l + (r - l)//2
if (L[m] >= key):
r = m
else:
l = m
return r
def LongestDecreasingSubsequenceLength(L, size):
tailTable = [0 for i in range(size + 1)]
len = 0
tailTable[0] = L[0]
len = 1
for i in range(1, size):
if (L[i] < tailTable[0]):
# new smallest value
tailTable[0] = L[i]
elif (L[i] > tailTable[len-1]):
tailTable[len] = L[i]
len+= 1
else:
tailTable[binary_search(tailTable, -1, len-1, L[i])] = L[i]
return len
L = [ 38, 20, 15, 30, 90, 14, 6, 7]
n = len(L)
print("Length of Longest Decreasing Subsequence is ",
LongestDecreasingSubsequenceLength(L, n))
如果您愿意以任何方式来看待它,那么您可以使用一些伪代码,这些伪代码可以轻松地转换为Python并翻转以减少子序列
N = len(X)
P = np.zeros(N, dtype=np.int)
M = np.zeros(N+1, dtype=np.int)
L = 0
for i in range(0, N-1):
# Binary search for the largest positive j ≤ L
# such that X[M[j]] <= X[i]
lo = 1
hi = L
while lo <= hi:
mid = (lo+hi)//2
if X[M[mid]] >= X[i]:
lo = mid+1
else:
hi = mid-1
# After searching, lo is 1 greater than the
# length of the longest prefix of X[i]
newL = lo
# The predecessor of X[i] is the last index of
# the subsequence of length newL-1
P[i] = M[newL-1]
M[newL] = i
#print(i)
if newL > L:
# If we found a subsequence longer than any we've
# found yet, update L
L = newL
# Reconstruct the longest increasing subsequence
S = np.zeros(L, dtype=np.int)
k = M[L]
for i in range(L-1, -1, -1):
S[i] = X[k]
k = P[k]
S
我不明白最长的递减子序列是什么?如果下一个列表较小,则增加列表,如果下一个列表较大,则存储列表,这不是更简单吗?在大多数情况下,这意味着某些测试的顺序错误,我认为这也不正确。。。你可以清楚地看到,最长的递减子序列是538,20,15,14,6Ah好的,不清楚这是你想要的。你能用预期的结果更新你的问题吗,以及为什么要这样做的更多的理由吗?这是如果您在最长的连续递减序列之后
array([38, 20, 15, 14, 6])