Java for LeetCode 006 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"

解题思路：

观察题目，靠眼力寻找规律即可。如果没有读懂ＺｉｇＺａｇ的话，请移步

http://blog.csdn.net/zhouworld16/article/details/14121477

java实现

static public String convert(String s, int nRows) {
        if (s == null || s.length() <= nRows || nRows <= 1)
            return s;

        StringBuffer sb = new StringBuffer();

        for (int i = 0; i < s.length(); i += (nRows - 1) * 2)
            sb.append(s.charAt(i));

        for (int i = 1; i < nRows - 1; i++) {
            for (int j = i; j < s.length(); j += (nRows - 1) * 2) {
                sb.append(s.charAt(j));
                if (j + (nRows - i - 1) * 2 < s.length()) {
                    sb.append(s.charAt(j + (nRows - i - 1) * 2));
                }
            }
        }

        for (int i = nRows - 1; i < s.length(); i += (nRows - 1) * 2)
            sb.append(s.charAt(i));

        return new String(sb);
    }