[Leetcode]6. ZigZag Conversion @python

题目

The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

P		A		H		N
A	P	L	S	I	I	G
Y		I		R

And then read line by line: “PAHNAPLSIIGYIR”
Write the code that will take a string and make this conversion given a number of rows:

string convert(string text, int nRows);
convert(“PAYPALISHIRING”, 3) should return “PAHNAPLSIIGYIR”.

题目要求

给定字符串text和字符串排列行数nRows，按照上图所示的方式对字符串按照列序进行排列，将排列好的字符串按行连接起来作为返回值。

解题思路

用一个数组来存储每一行的字符，用变量row来记录当前访问到的行，依次将字符串text中的字符放入不同的行，然后将所有行的字符串串联起来。

代码

class Solution(object):
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        if numRows == 1:
            return s
        zigzag = ['' for _ in range(numRows)]
        row = 0
        step = 1
        for c in s:
            if row == 0:
                step = 1
            if row == numRows - 1:
                step = -1
            zigzag[row] += c
            row += step
        return ''.join(zigzag)