Python-Leetcode/6.ZigZagConversion.py at master · tcoln/Python-Leetcode · GitHub

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"""
若numRows == 1，直接返回字符串s
否则：
·若是第一行：依次向down走到底，然后向up走到顶，取字符
·若是中间行：依次从每行的第一个字符开始，先分别向down走到底，然后向up走到顶，取字符；反向走取字符；
·若是最后一行：先up到顶后down到底，取字符。
"""
class Solution(object):
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        #numRows = 4
        l = len(s)
        if numRows == 1:
            return s
        a = ''
        for i in range(numRows):
            j = i
            step = 0 if i != numRows-1 else 1
            while(j < l):
                a += s[j]
                if step % 2 == 0:
                    if i == 0:
                        step += 1
                    down = numRows - (i+1)
                    up = numRows - (i+1)
                    j += down + up
                else:
                    if i == numRows-1:
                        step += 1
                    up = i
                    down = i
                    j += up + down
                step += 1
        return a