锯齿形的转换 字符串“paypalishiring”写的是在一个给定的行数，这样一个曲折的模式：（你可能想在一个固定的字体更加易读显示模式）(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 fon