leetcode 6 ZigZag Conversion

2017-05-10

leetcode 6 ZigZag Conversion

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”.

题目大概意思是：给定字符串text和行数nRows，对字符串按照列进行排列，将排列好的字符串按行连接起来作为返回值。

“abcdefghijklmnopqrstuvwxyz”,4

a g m s y
b f h l n r t x z
c e i k o q u w
d j p v

“abcdefghijklmnopqrstuvwxyz”,5

a i q y
b h j p r x z
c g k o s w
d f l n t v
e m u

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。

# coding:utf-8
class Solution(object):
	def convert(self, s, numRows):
		if numRows == 1:
			return s
		zigzag = ['' for i 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)


if __name__ == "__main__":
	so = Solution()
	print so.convert("", 1)
	print so.convert("PAYPALISHIRING", 3)
	print so.convert("abcdefghijklmnopqrstuvwxyz", 4)
	print so.convert("abcdefghijklmnopqrstuvwxyz", 5)

参考 Leetcode 6. ZigZag Conversion @python