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".

 

即写成z字型，假设字符串是ABCDEFGHIJK，行数是5，则转换为

A           I

B       H J

C    G    K 

D F

E

 

class Solution {

    public 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 idx = 0; idx < numRows && i < len; idx++)

                sb[idx].append(c[i++]); //原字符串从上往下加入到StringBuffer中

            for (int idx = numRows-2; idx >= 1 && i < len; idx--)

                sb[idx].append(c[i++]); //原字符串从下往上加入到StringBuffer中

        }

        for (int idx = 1; idx < sb.length; idx++)

            sb[0].append(sb[idx]);

        return sb[0].toString();

    }

}

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