6. Z字形变换（ZigZag Conversion）

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)
将字符串 “PAYPALISHIRING” 以Z字形排列成给定的行数：

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:
之后从左往右，逐行读取字符：”PAHNAPLSIIGYIR”
实现一个将字符串进行指定行数变换的函数:

string convert(string s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"

Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

解答：

class Solution {
    public String convert(String s, int numRows) {
        char[] ch = s.toCharArray();
        int in = numRows*2,ln, sum = 2*numRows - 2;
        int te=-1;
        StringBuilder ss = new StringBuilder();
        ss.append("");
        int tt = numRows;
        while(tt-- != 0){
            in = in-2;
            if(in == 0){
                in = sum;
            }
            te++;
            int ff = 0;
            ln = in;
            if(ln == 0){
                ln = 1;
            }
            for(int i=te;i<ch.length;i+=ln){
                // System.out.print(ch[i]);
                ss.append(ch[i]);

                if(ff == 1 && ln < sum){
                    ln = 2*numRows - 2 - ln;
                    ff = 1;
                }
                // for(int j=0;j<ln-1;j++){
                //     System.out.print(" ");
                // } 
                ff = 1;

            }
            System.out.println();
        }
        return ss.toString();

    }
}

这个题我曾经调试了很久，反复检查，代码是正确的但系统就是判定失败。最后我终于找到了原因……不需要输出 Z 字形排列的图形，所以把代码里打印图形的代码注释掉就OK啦~