ZigZag Conversion

leetcode中的曲折转换问题

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"

.

代码如下：

public class ZigZagConversion {

public String convert(String s, int nRows){
char[] c = s.toCharArray();
int len = c.length;
StringBuffer[] sb = new StringBuffer[nRows];

for(int i = 0; i < sb.length; i++)
sb[i] = new StringBuffer();

int i = 0;
while(i < len){
//垂直向下
for(int idx = 0; idx < nRows && i < len; idx++){
sb[idx].append(c[i++]);
}
//斜向上
for(int idx = nRows - 2; idx >= 1 && i < len; idx--){
sb[idx].append(c[i++]);
}
}

//组合成一个string
for(int idx = 1;idx < sb.length; idx++){
sb[0].append(sb[idx]);
}

return sb[0].toString();

}

}