题目：实现一个trim()函数，去除字符串首尾的空格（不能使用strip()方法）
例：
1.字符串为空的情况，输入trim(’ ‘) 预期返回结果 ‘’
2.字符串首尾空格数大于1的情况，输入trim(’ a bc ') 预期返回结果 ‘a bc’
4 个赞
正则解法如下：
import re
def trim(s):
return re.sub(r'^(\s+)|(\s+)$', '',s)
正则解释：
^(\s+) 表示匹配以空格开头的字符串
(\s+)$ 表示匹配以空格结尾的字符串
| 表示或的意思
附录：
解法1：分别找到首位非空格的元素的下标，然后切片
def trim1(string):
cursor_l = 0
cursor_r = 0
for i in range(len(string)):
if string[i] != ' ':
cursor_l = i
print(cursor_l)
break
for i in range(len(string)):
if string[::-1][i] != ' ':
cursor_r = len(string)-i
break
return string[cursor_l:cursor_r]
思路2：先替换所有空格得到子串，再去原字符串中定位找字串首位元素的切片
def trim2(string):
sub = string.replace(' ', '')
return string[string.find(sub[0]):string.rfind(sub[-1]) + 1]
def trim(super):
a = 0
b = 0
for i in range(len(super)):
if super[i] == ' ':
a += 1
else:
break
for i in range(len(super)):
if super[-(i+1)] == ' ':
b += 1
else:
break
print(a,b)
print(super[a:-b])
trim(' 23 2 1231 123 ')def trim(str_):
start = 0
while start + 1 < len(str_) and str_[start] == " ":
start += 1
end = len(str_)
while end > start and str_[end-1] == " ":
end -= 1
return str_[start:end]
test1 = " ab c "
test2 = " ab"
test3 = "ab "
test4 = " "
test5 = ""
assert trim(test1) == "ab c"
assert trim(test2) == "ab"
assert trim(test3) == "ab"
assert trim(test4) == ""
assert trim(test5) == ""
棒棒的！
棒棒的！相信跟你对接的研发肯定很幸福，用例很到位！
def trim(super):
a = 0
b = 0
for i in range(len(super)):
if super[i] == ' ':
a += 1
else:
break
for i in range(len(super)):
if super[-(i+1)] == ' ':
b += 1
else:
break
if b==0:
return super[a:]
else:
return super[a:-b]
assert trim('abc') == 'abc'
assert trim('a b c') == 'a b c'
assert trim(' abc ') == 'abc'
assert trim(' abc') == 'abc'
assert trim('abc ') == 'abc'
assert trim(' abc ') == 'abc'
assert trim(' a b c ') == 'a b c'def trim(str):
head = 0
tail = len(str) - 1
for i in range(len(str)):
if str[i] == " ":
head += 1
else:
break
for i in range(len(str)-1, 0, -1) and str[i] == " ":
if str[i] == " ":
tail -= 1
else:
break
return str[head: tail+1]
assert trim('abc') == 'abc'
assert trim('a b c') == 'a b c'
assert trim(' abc ') == 'abc'
assert trim(' abc') == 'abc'
assert trim('abc ') == 'abc'
assert trim(' abc ') == 'abc'
只适用于前后最多只有一个空格符号
def trimB(s:str):
L = list(s)
countF,countB = 0,0
for item in L:
if item == ' ':
countF += 1
else:
break
L.reverse()
for item in L:
if item == ' ':
countB += 1
else:
break
return ''.join(list(s)[countF:len(L)-countB])
def trim(string):
list0 = []
list1 = []
sep = ''
for i in string:
list0.append(i)
for num in range(len(list0)):
if list0[num] != ' ':
list1.append(num)
try:
num1 = list1[0]
num2 = list1[-1]
if (num1, num2 == True) and num1 != num2:
result = sep.join(string[num1])
for k in range(int(list1[0]), int(list1[-1])):
num1 += 1
result = result + string[num1]
print(result)
except:
print('')
trim(' ')
trim(' adfs 4546 sfsdfj ')
def trim(s:str) ->str:
lis = list(s)
start = 0
end = 0
for i in range(len(s)):
if " " != lis[i]:
start = i
break
else:
continue
lis.reverse()
for i in range(len(s)):
if " " != lis[i]:
end = i
break
if end == 0:
return s[start:]
return s[start:-end]
def Str(str):
start = [0,0]
for i in range(len(str)):
if str[i] == ' ':
start[0] +=1
else:
break
for i in range(len(str)):
if str[-(i+1)] == ' ':
start[1]+=1
else:
break
a = start[0]
b = start[1]
if b == 0:
str1 = str[a:]
else:
str1 = str[a:-b]
return str1
str = 'a bc'
test1 = " ab c "
test2 = " ab"
test3 = "ab "
test4 = " "
test5 = ""
print("str =",Str(str))
print("test1 =",Str(test1))
print("test2 =",Str(test2))
print("test3 =",Str(test3))
print("test4 =",Str(test4))
print("test5 =",Str(test5))
def trim(s: str):
left_cut=0
right_cut=0
for i in range(len(s)):
if s[i]==' ':
left_cut+=1
else:
break
for j in range(len(s)):
if s[::-1][j]==' ':
right_cut-=1
else:
break
return s[left_cut:right_cut]
assert trim(' ')==''
assert trim(' a bc ')=='a bc'