有更好的算法但愿指正，最长回串python
def get_long_str(s):
l = list(s)
result = dict()
print(l.count(l[0]),len(l))
if len(s) <= 1:
return s
elif l.count(l[0]) == len(l):
return s
else:
for i in range(0, len(l)):
for j in range(i + 1, len(l)):
if l[i] == l[j]:
if j + 1 - i in result.keys():
pass
else:
tmp,tmp_b = l[i:j+1],l[i:j+1]
tmp_b.reverse()
if tmp==tmp_b:
result[j + 1 - i] = l[i:j + 1]
i =j
else:
continue
if len(result) == 0:
return s[0]
else:
return ''.join(result[max(result.keys())])