[LeetCode] #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".

程序很简单第一排和最后一排是一组公式，2*nRows-2，，其他排用另一组公式，分奇偶，公式分别是2 * (nRows - i - 1)和2 * i 。时间：29ms

代码如下：

class Solution {
public:
    string convert(string s, int nRows) {
        if (nRows <= 1 || s.size() == 0)
            return s;
        string str;
        for (int i = 0; i < s.size() && i < nRows; i++){
            int j = i, x=1;
            while (j < s.size()){
                str += s[j];
                if (i == 0 || i == nRows-1)
                    j += 2 * nRows - 2;
                else{
                    if (x & 0x1)
                        j += 2 * (nRows - i - 1);
                    else
                        j += 2 * i;
                    x++;
                }
            }
        }
        return str;
    }
};