[leetcode]ZigZag Conversion @ Python

原题地址：https://oj.leetcode.com/problems/zigzag-conversion/

题意：

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".

解题思路：字符串处理，没什么知识点，需要一点编程技巧。

代码：

class Solution:
    # @return a string
    def convert(self, s, nRows):
        if nRows==1: return s
        tmp=['' for i in range(nRows)]
        index=-1; step=1
        for i in range(len(s)):
            index+=step
            if index==nRows:
                index-=2; step=-1
            elif index==-1:
                index=1; step=1
            tmp[index]+=s[i]
        return ''.join(tmp)