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题目描述
牛客最近来了一个新员工Fish,每天早晨总是会拿着一本英文杂志,写些句子在本子上。同事Cat对Fish写的内容颇感兴趣,有一天他向Fish借来翻看,但却读不懂它的意思。例如,“student. a am I”。后来才意识到,这家伙原来把句子单词的顺序翻转了,正确的句子应该是“I am a student.”。Cat对一一的翻转这些单词顺序可不在行,你能帮助他么?
思路及Python实现
用字符的翻转
class Solution:
def reverse(self, s):
start = 0
end = len(s) - 1
while start < end:
s[start], s[end] = s[end], s[start]
start += 1
end -= 1
def ReverseSentence(self, s):
s = list(s.split(" "))
self.reverse(s)
return " ".join(s)
obj = Solution()
print(obj.ReverseSentence(" "))
利用栈,先装入,再倒出来
class Solution:
def ReverseSentence(self, s):
# write code here
if s == " ":
return s
stack=[]
new_s=s.split(" ")
for item in new_s:
stack.append(item)
ret=[]
while stack:
ret.append(stack.pop())
return " ".join(ret)
先将整个字符串翻转,然后再根据空格,对每个单词翻转,结束之后,就是正常序列的字符串了
class Solution:
def reverse(self,s,start,end):
while start < end:
s[start],s[end] = s[end],s[start]
start += 1
end -= 1
return s
def ReverseSentence(self, s):
if len(s) <= 1:
return s
strlist = []
for i in range(len(s)):
strlist.append(s[i])
self.reverse(strlist,0,len(strlist)-1)
start = 0
end = 0
for i in range(len(strlist)):
# 这样写是先将最后一个空格之间的单词给翻转,最后一个单词不会翻转。
if strlist[i] == " ":
end = i
self.reverse(strlist,start,end-1)
start = i + 1
self.reverse(strlist,start,len(strlist)-1)
# 单独对最后一个单词翻转,要不然最后一个单词仍然是倒叙
return "".join(strlist)