給定字元陣列chars，在單詞間逆序，對空格位置沒有特別要求。
例如：
『dog loves pig』
-> 『gip sevol god』
-> 『pig loves dog』
先整體逆序，再按單詞逆序。
def
reverse
(chars, beg, end)
:while beg < end:
chars[beg]
, chars[end-1]
= chars[end-1]
, chars[beg]
beg +=
1 end -=
1def
rotate_by_word
(s):
if s is
none
:return s
chars =
list
(s) reverse(chars,0,
len(chars)
) begin, end =-1
,-1for i in
range
(len
(chars)):
c = chars[i]
if c !=
' ':
if begin ==-1
: begin = i
else
: end = i
if i ==
len(chars)-1
: end =
len(chars)
if begin !=-1
and end !=-1
: reverse(chars, begin, end)
begin, end =-1
,-1return
''.join(c for c in chars)
def
rotate_by_word2
(s):
s = s[::
-1]return
' '.join(a[::
-1]for a in s.split(
))
def
test_reverse()
: s =
'abcdef'
chars =
list
(s) reverse(chars,0,
len(chars)
) r =
''.join(chars)
r1 = s[::
-1] r2 =
''.join(
reversed
(s))
assert
(r == r1)
assert
(r == r2)
print
('test reverse done'
)def
test_rotate_by_word()
:assert
(rotate_by_word(
'abc def')==
'def abc'
)assert
(rotate_by_word(
'dog loves pig')==
'pig loves dog'
)assert
(rotate_by_word(
"i'm a student.")==
"student. a i'm"
)assert
(rotate_by_word2(
'abc def')==
'def abc'
)assert
(rotate_by_word2(
'dog loves pig')==
'pig loves dog'
)assert
(rotate_by_word2(
"i'm a student.")==
"student. a i'm"
)print
('test rotate by word done'
)
牛客網
給定字元陣列chars，和乙個整數size，把大小為size的左半區整體移到右半區，右半區移到左半區。
例如：『abcde』 size = 3
-> 『deabc』
『abcde』
-> 『cbaed』
-> 『deabc』
先按size分成兩部分，兩部分分別逆序，然後整體逆序
def
rotate_k
(s, k)
:if s is
none
orlen
(s)< k:
return s
chars =
list
(s) reverse(chars,
0, k)
reverse(chars, k,
len(chars)
) reverse(chars,0,
len(chars)
)return
''.join(c for c in chars)
def
rotate_k2
(s, k)
:return s[k:
]+ s[
:k]
『1234567abcd』 size = 7
def
rotate_k3
(s, k)
:def
exchange
(chars, begin, end, size)
: i = end - size
for _ in
range
(size)
: chars[begin]
, chars[i]
= chars[i]
, chars[begin]
begin +=
1 i +=
1if s is
none
orlen
(s)< k:
return s
chars =
list
(s) begin, end =0,
len(s)
left, right = k,
len(s)
-k while
true
: d = left - right
s =min(left, right)
exchange(chars, begin, end, s)
if d ==0:
break
elif d <0:
end -= s
right =
-d elif d >0:
begin += s
left = d
return
''.join(chars)
def
test_rotate_k()
:assert
(rotate_k(
'abcde',3
)=='deabc'
)assert
(rotate_k2(
'abcde',3
)=='deabc'
)assert
(rotate_k3(
'1234567abcd',7
)=='abcd1234567'
)print
('test rotate k done'
)if __name__ ==
'__main__'
: test_reverse(
) test_rotate_k(
) test_rotate_by_word(
)
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