[6] ZigZag Conversion

https://leetcode.com/problems/zigzag-conversion/description/

• algorithms
• Medium (29.34%)
• Source Code: 6.zigzag-conversion.py
• Total Accepted: 305.2K
• Total Submissions: 974.2K
• Testcase Example: '"PAYPALISHIRING"\n3'

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 s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3 Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4 Output: "PINALSIGYAHRPI" Explanation:

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

class Solution(object):
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        if numRows == 1: return s
        result = [['' for i in range(len(s))] for j in range(numRows)]
        i, j = 0, 0
        direction = 'down'
        for char in s:
            result[i][j] = char
            if direction == 'down':
                if i == numRows - 1:
                    direction = 'up'
                    i -= 1
                    j += 1
                else:
                    i += 1
            else:
                if i == 0:
                    direction = 'down'
                    i += 1
                else:
                    i -= 1
                    j += 1
        ret = ''
        for r in result:
            ret += ''.join(r)
        return ret
#
#
# if __name__ == '__main__':
#     s = Solution()
#     print(s.convert("ABC", 2))