【Leetcode Algorithm】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".

这道题题目给的不太明白，容易让不清楚ZigZag的人一头雾水，下面这个大家已看应该就清楚了

Zigzag:即循环对角线结构（

0				8				16
1			7	9			15	17
2		6		10		14		18
3	5			11	13			19
4				12				20

）

 

向下循环:nRows

斜角线循环:nRows-2(减去首尾两个端点)

重复

代码：

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public class Solution {     public String convert(String s, int numRows) {         StringBuffer sb = new StringBuffer();         if(numRows<2){             return s;         }         else{             //两列直接的对角线元素为numRows-2；因此定义两列之间的步长             int step = 2*(numRows-1);             for(int row=0;row<numRows;row++){                 //按照步长将第row行的非对角线元素添加进StringBuffer                 for(int j=row;j<s.length();j+=step){                     sb.append(s.charAt(j));                     //当第row行不是首行和尾行，且增加步长之后的索引在长度范围内时，将对角线上的元素添加到StringBuffer                     if((row!=0&&row!=numRows-1)&&(j+step-row*2)<s.length()){                         sb.append(s.charAt(j+step-row*2));                     }                 }             }             return sb.toString();         }     } }