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reverse-string-ii.py
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reverse-string-ii.py
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# Time: O(n)
# Space: O(1)
# Given a string and an integer k, you need to reverse the first k characters
# for every 2k characters counting from the start of the string.
# If there are less than k characters left, reverse all of them.
# If there are less than 2k but greater than or equal to k characters,
# then reverse the first k characters and left the other as original.
# Example:
# Input: s = "abcdefg", k = 2
# Output: "bacdfeg"
# Restrictions:
# The string consists of lower English letters only.
# Length of the given string and k will in the range [1, 10000]
# V0
# V1
# http://bookshadow.com/weblog/2017/03/12/leetcode-reverse-string-ii/
class Solution(object):
def reverseStr(self, s, k):
"""
:type s: str
:type k: int
:rtype: str
"""
ans = ''
round = int(math.ceil(len(s) / (2.0 * k)))
for x in range(round):
ans += s[x * 2 * k : (x * 2 + 1) * k][::-1]
ans += s[(x * 2 + 1) * k : (x * 2 + 2) * k]
return ans
# V2
class Solution:
def reverseStr(self, s, k):
list_s = list(s)
for i in range(0,len(list_s), 2*k):
list_s[i:i+k] = reversed(list_s[i:i+k])
return ''.join( str(j) for j in list_s)
# V2'
class Solution(object):
def reverseStr(self, s, k):
"""
:type s: str
:type k: int
:rtype: str
"""
s = list(s)
for i in range(0, len(s), 2*k):
s[i:i+k] = reversed(s[i:i+k])
return "".join(s)