【LeetCode】6. ZigZag Conversion

1.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)

将一个给定字符串根据给定的行数，以从上往下、从左到右进行 Z 字形排列。

比如输入字符串为 "PAYPALISHIRING" 行数为 3 时，排列如下：

P   A   H   N
A P L S I I G
Y   I   R

And then read line by line: "PAHNAPLSIIGYIR"

之后，你的输出需要从左往右逐行读取，产生出一个新的字符串，比如："PAHNAPLSIIGYIR"

Write the code that will take a string and make this conversion given a number of rows:

string convert(string s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

2.Solutions

public static String convert(String s, int numRows) {
    char[] c = s.toCharArray();
    int len = c.length;
    StringBuffer[] sb = new StringBuffer[numRows];
    for (int i = 0; i < sb.length; i++)
        sb[i] = new StringBuffer();

    int i = 0;
    while (i < len) {
        for (int row = 0; row < numRows && i < len; row++)
            sb[row].append(c[i++]);// vertically down 垂直向下

        for (int row = numRows - 2; row >= 1 && i < len; row--) {
            sb[row].append(c[i++]);// obliquely up 斜向上
        }
    }
    for (int row = 1; row < sb.length; row++)
        sb[0].append(sb[row]);

    return sb[0].toString();
}

（完）