Zigzag Conversion

题目描述

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".

解题方法

建立一个2d array，按照顺序将字母加到这个array里，然后再按行输出就可以了。

Solution

class Solution(object):
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        if numRows == 1 or numRows >= len(s):
            return s

        zigzag = [[] for i in range(numRows)]

        row, step = 0, 1
        for c in s:
            zigzag[row].append(c)
            if row == 0:
                step = 1
            elif row == numRows - 1:
                step = -1
            row += step

        result = ""
        for i in range(numRows):
            result += "".join(zigzag[i])

        return result

Reference