ZigZag Conversion

1.题目

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".

2.算法

发现所有行的重复周期都是 2 * nRows - 2，对于首行和末行之间的行，还会额外重复一次，重复的这一次距离本周期起始字符的距离是 2 * nRows - 2 - 2 * i

public String convert(String s, int nRows) {if (s == null || s.length() == 0 || nRows <= 0){return "";}StringBuilder sb = new StringBuilder();int size = 2 * nRows - 2;for (int i = 0; i < nRows; i++){for (int j = i; j < s.length(); j += size){sb.append(s.charAt(j));if (i != 0 && i != nRows - 1 && j + size - 2 * i < s.length()){sb.append(j + size - 2 * i);}}}return sb.toString();}