LeetCode-6 ZigZag Conversion(字符串锯齿形输出)

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"

.

public class Solution {
	public static void main(String[] args) {
		System.out.println(convert("PAYPALISHIRING", 3));
	}

	public static String convert(String s, int nRows) {
		if (nRows==1) {
			return s;
		}
		char[] schar = s.toCharArray();//后面使用字符的部分改成s.charAt就也可以不开辟这个数组
		String output = "";
		int grouplen = 2 * (nRows - 1);
		//①.每2n-2个元素为一组，数组中第0位和第nrow-1位只有一个输出，其他位置每次都输出两个（前提是数组不越界）。
		int groupnum = s.length() / grouplen + 1;
		for (int j = 0; j < nRows; j++) {
			for (int i = 0; i < groupnum; i++) {
				if ((grouplen * i + j) < s.length() ) {
					output += schar[grouplen * i + j];
					if (j != 0 && j != nRows-1 && ((i+1)*grouplen - j) < s.length() ) {//①
						output += schar[((i+1)*grouplen - j)];
					}
				}
			}
		}
		return output;
	}
}

Runtime：478 ms

分析：

见代码注释，主要就是分组的方法，然后对多组元素位置遍历。