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   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”.

---

思路：

1. 先定义一个数组array的长度和宽度，我按最长的长度定义的为s.length()/2+1;
2. 将字符串中的字符逐个按 ‘z’ 字形添加到数组中，注意调整col和row;
3. 定义一个StringBuilder sb,逐行扫描数组array，将每一个字符都追加到sb中。
4. 返回sb;

//  6. ZigZag Conversion    public String convert(String s, int numRows) {        if(s==null || s.equals("") || numRows==1) return s;//        int cols = (s.length()*2)/(numRows+1);        int cols = s.length()/2+1;        int rows = numRows;        char[][] array= new char[rows][cols];        int col = 0;        int row = 0;        boolean flag = false;//        按Z字形放到数组中        for(int i= 0;i<s.length();i++){            if(flag){                array[row--][col++] = s.charAt(i);                if(row == 0){                    row = 0;                    flag = false;                }            }else{                array[row++][col] = s.charAt(i);                if(row == numRows){                    flag = true;                    row -= 2;                    col++;                }                if(row == 0){                    flag = false;                    row = 0;                }            }        }        //开始打印        StringBuilder sb = new StringBuilder();        for(int i = 0;i<rows;i++){            for(int j = 0;j<cols;j++){                if(array[i][j]!=0){                    sb.append(array[i][j]);                }            }        }        return sb.toString();    }

测试用例：

    @Test    public void convertTest(){        println(s.convert("PAYPALISHIRING", 3));        println(s.convert("PAYPALISHIRING", 4));        println(s.convert("PAYPALISHIRING", 2));        println(s.convert("PAYPALISHIRING", 1));    }

输出结果：

PAHNAPLSIIGYIRPINALSIGYAHRPIPYAIHRNAPLSIIGPAYPALISHIRING