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https://github.com/SunnyQjm/algorithm-review.git
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86 lines
2.5 KiB
Python
86 lines
2.5 KiB
Python
#!/usr/bin/env python
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# coding=utf-8
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############################################################
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# Z 字形变换
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# 将一个给定字符串根据给定的行数，以从上往下、从左到右进行 Z 字形排列。
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# 比如输入字符串为 "LEETCODEISHIRING" 行数为 3 时，排列如下：
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# L C I R
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# E T O E S I I G
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# E D H N
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# 之后，你的输出需要从左往右逐行读取，产生出一个新的字符串，比如："LCIRETOESIIGEDHN"。
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# 请你实现这个将字符串进行指定行数变换的函数：
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# string convert(string s, int numRows);
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#
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# 示例 1：
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# 输入: s = "LEETCODEISHIRING", numRows = 3
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# 输出: "LCIRETOESIIGEDHN"
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#
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# 示例 2:
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# 输入: s = "LEETCODEISHIRING", numRows = 4
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# 输出: "LDREOEIIECIHNTSG"
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# 解释:
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#
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# L D R
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# E O E I I
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# E C I H N
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# T S G
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############################################################
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import collections
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class Solution:
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def convert(self, s, numRows):
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"""
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:type s: str
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:type numRows: int
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:rtype: str
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(Knowledge)
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算法思路:
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1. 用numRows个list记录每行的字符串；
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2. 然后顺序遍历字符串，按Z字形顺序放到合适的行中；
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3. 最后将每行的字符串拼接即可
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"""
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if numRows == 1:
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return s
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lines = [[] for i in range(numRows)]
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# 当前的方向（首先向下，触底向上，触顶向下，依次改变方向）
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goDown = True
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# 下一个字符要写入的行号，初始为0,根据方向进行更新，向下则+1,向上则-1
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lineNumber = 0
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# 依次遍历字符串，按Z字型顺序写到合适的行
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for i in range(len(s)):
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lines[lineNumber].append(s[i])
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# 判断是否需要改变方向
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if goDown and lineNumber == numRows - 1:
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goDown = False
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if not goDown and lineNumber == 0:
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goDown = True
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# 根据当前的方向更新行号
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lineNumber = lineNumber + 1 if goDown else lineNumber - 1
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# 将所有numRows个list拼接成一个list
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for i in range(1, numRows):
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lines[0] += lines[i]
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# 将list转字符串返回
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return "".join(lines[0])
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if __name__ == '__main__':
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solution = Solution()
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print(solution.convert("LEETCODEISHIRING", 3), "= \nLCIRETOESIIGEDHN")
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print(solution.convert("LEETCODEISHIRING", 4), "= \nLDREOEIIECIHNTSG")
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