PAYPALISHIRING   P   A   H   NA P L S I I GY   I   R

import java.util.Arrays;/** * * * convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR". * *   P   A   H   N   A P L S I I G   Y   I   R */public class ZigZagConversion {    public static void main(String[] args) {        ZigZagConversion zzc = new ZigZagConversion();        System.out.println(zzc.convert("PAYPALISHIRING",3));;    }    public String convert(String s, int nRows) {        int len = s.length();        if (len == 0 || nRows <= 1) return s;        String[] ans = new String[nRows];//使用n行的数组存储结果        Arrays.fill(ans, "");        int row = 0, delta = 1;        for (int i = 0; i < len; i++) {            ans[row] += s.charAt(i);//            System.out.println("row:"+row+",ans["+row+"]:"+ans[row]+",i:"+i);            row += delta;//            System.out.println("^^^"+row);            if (row >= nRows) {                row = nRows-2;  //最底层的上一层                delta = -1;     //到达最底层之后,逐级递升//                System.out.println("---"+row+","+i+"---");            }            if (row < 0) {                row = 1;        //第二层                delta = 1;      //逐级深入下一层//                System.out.println("***"+"1,"+i+"***");            }        }        String ret = "";        for (int i = 0; i < nRows; i++) {            ret += ans[i];        }        return ret;    }}//    /**//     * 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) {//        int len = s.length();//        if (len == 0 || nRows < 2) return s;////        String ret = "";//        int lag = 2*nRows - 2; //循环周期//        for (int i = 0; i < nRows; i++) {//            for (int j = i; j < len; j += lag) {//                ret += s.charAt(j);//                //非首行和末行时还要加一个//                if (i > 0 && i < nRows-1) {//                    int t = j + lag - 2*i;//                    if (t < len) {//                        ret += s.charAt(t);//                    }//                }//            }//        }//        return ret;//    }