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   NA P L S I I GY   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".

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

思路：找规律。每个zigzag是2*rows-1个字符。

public class Solution {	public String convert(String s, int nRows) {		if (nRows == 1)			return s;		StringBuilder sb = new StringBuilder();		int len = s.length();		for (int i = 0; i < nRows; i++) {			if (i == 0 || i == nRows - 1) {				int j = i;				while (j < len) {					sb.append(s.charAt(j));					j += 2 * nRows - 2;				}			} else {				int j = i;				int k = 2 * nRows - 2 - i;				while (j < len || k < len) {					if (j < len)						sb.append(s.charAt(j));					if (k < len)						sb.append(s.charAt(k));					j += 2 * nRows - 2;					k += 2 * nRows - 2;				}			}		}		return sb.toString();	}	public static void main(String[] args) {		System.out.println(new Solution().convert("PAYPALISHIRING", 3));		System.out.println(new Solution().convert("abcdefghijklmn", 5));		System.out.println(new Solution().convert("abcdefghijklmn", 4));		System.out.println(new Solution().convert("abcdefghijklmn", 1));	}}

参考：

http://fisherlei.blogspot.com/2013/01/leetcode-zigzag-conversion.html

http://blog.csdn.net/linhuanmars/article/details/21145039