z型转换

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”.

解题方案:

这道题目比较简单，就不做分析了，直接贴代码。

    public String convert(String s, int numRows) {
        StringBuffer[] sbs = new StringBuffer[numRows];
        for (int i = 0; i < sbs.length; i++) {
            sbs[i] = new StringBuffer();
        }
        int flag = 0;
        int step = -1;
        for (int i = 0; i < s.length(); i++) {
            sbs[flag].append(s.charAt(i));
            if (flag == numRows - 1 || flag == 0) {
                step = -step;
            }
            flag += step;
            if (flag < 0) {
                flag = 0;
            }
            if (flag > numRows - 1) {
                flag = numRows - 1;
            }
        }

        StringBuffer result = new StringBuffer();
        for(StringBuffer sb : sbs) {
            result.append(sb);
        }
        return result.toString();
    }