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   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"

public class Solution {    public String convert(String s, int numRows) {        StringBuffer[] sb = new StringBuffer[numRows];        for(int i = 0; i < sb.length; i++){            sb[i] = new StringBuffer();        }        int len = s.length();        int i = 0;        while(i < len){            for(int j = 0; j < numRows && i < len; j++){                sb[j].append(s.charAt(i++));            }            for(int j = numRows - 2; j > 0 && i < len; j--){                sb[j].append(s.charAt(i++));            }        }        for(int k = 1; k < numRows; k++){             sb[0].append(sb[k]);        }                   return sb[0].toString();    }   }

解析如下图所示（自己手画的）：