Question

如何使用python确定同一字母的最长序列？

例如，我使用以下代码来打印具有3个条件A，B和C的混洗列表

from random import shuffle
condition = ["A"]*20
condition_B = ["B"]*20
condition_C = ["C"]*20

condition.extend(condition_B)
condition.extend(condition_C)
shuffle(condition)
print(condition)

现在，我要确保同一条件连续发生的次数不超过三次。

例如，允许：[A，B，C，A，B，B，C，C，C，A，B…。] 不允许：[A，A，B，B，B，B，C，A，B ...]（因为连续有四个B）

如何解决此问题？预先谢谢你。

Answer 1

也许您应该按顺序构建列表，而不是改组：

result = []
for i in range(60):     # for each item in original list
  start = true          # we haven't found a suitable one yet
  if start or i>2:      # don't do checking unless 3 items in list
    while start or (
           c==shuf[-1] and     # is the chosen value
           c==shuf[-2] and     # the same as any of
           c==shuf[-3] ):      # the last 3 items?
      idx = random.randint(0,len(condition))  # chose a new one
      c = condition[idx]
      start = false            
  result.append(c)      # add to result
  del condition[i]      # remove from list

警告！未经测试-只是概念性的...

Answer 2

# Validate with this function it return false if more than three consecutive characters are same else True.


def isValidShuffle( test_condition):

    for i in range(len(test_condition)-4):
        if len(set(test_condition[ i:i+4])) == 1:
            # set size will be 1 all four consecutive chars are same
            return False
    return True

创建isValidShuffle将返回True的A，B，C混合序列的最简单方法。

from random import shuffle

# condition list contains 20 A's 20 B's 20 C's

seq = ['A','B','C']
condition = []

for seq_i in range(20):
    shuffle(seq)
    condition += seq

print(condition) # at most two consecutive characters will be same 

print(isValidShuffle(condition))

-----------------------------------------------------------------------------

Output
['A', 'B', 'C', 'B', 'C', 'A', 'C', 'B', 'A', 'C', 'B', 'A', 'C', 'A', 'B', 'C', 'B', 'A', 'B', 'A', 'C', 'B', 'C', 'A', 'B', 'C', 'A', 'C', 'A', 'B', 'B', 'C', 'A', 'B', 'A', 'C', 'A', 'B', 'C', 'C', 'A', 'B', 'A', 'B', 'C', 'B', 'A', 'C', 'C', 'A', 'B', 'B', 'C', 'A', 'B', 'A', 'C', 'A', 'B', 'C']

............................................... ................................................... ................................................... ............
这在创建混排序列时没有施加您的限制，但是会继续尝试直到找到满足您连续字符限制的序列。

validshuffle = False 

condition = ['A']*20 + ['B']*20 + ['C']*20

while not validshuffle:

    shuffle(condition)

    if isValidShuffle(condition):
        validshuffle = True

print(condition)

-------------------------------------------------------------------------------
Output

try
try
['A', 'C', 'A', 'B', 'B', 'C', 'B', 'C', 'A', 'C', 'A', 'C', 'B', 'B', 'B', 'C', 'A', 'A', 'B', 'C', 'A', 'A', 'B', 'B', 'C', 'B', 'B', 'C', 'B', 'C', 'C', 'B', 'A', 'B', 'B', 'A', 'C', 'A', 'A', 'C', 'A', 'C', 'B', 'C', 'A', 'A', 'C', 'A', 'C', 'A', 'C', 'B', 'B', 'B', 'A', 'B', 'C', 'A', 'C', 'A']

Answer 3

如果您只想知道最长的子序列有多长时间，则可以执行此操作。这是在序列上进行迭代，并记录相同字符的子序列的长度，将其保存，获取每个子序列的最大值，然后获取字符的最大值。

这并不是您提到的问题，但它可能很有用。

from random import shuffle

sequence = ['A']*20 + ['B']*20 + ['C']*20 
sequences = {'A': [], 'B':[], 'C':[]}
shuffle(sequence)
current = sequence[0]
acc = 0
for elem in sequence:
    if elem == current:
        acc += 1
    else:
        sequences[current].append(acc)
        current = elem
        acc = 1
else:
    sequences[current].append(acc)
for key, seqs in sequences.items():
    sequences[key] = max(seqs)
print(max(sequences.items(), key=lambda i: i[1]))

如何使用python

3 个答案: