LeetCode-ZigZag Conversion

package com.leetcode.study;


public class Main {
    private int lo,maxLen;

    public static void main(String[] args) {
        String s = "AB";
        System.out.println(convert(s, 2));
        

    }
    public static String convert(String s, int numRows){
        if(numRows==1)return s;
        int len = s.length();
        if(numRows==2){
            StringBuffer sb1 = new StringBuffer();
            StringBuffer sb2 = new StringBuffer();
            for(int i = 0;i<len;i++){
                if(i%2==1)sb1.append(s.charAt(i));
                else sb2.append(s.charAt(i));
            }
            return sb2.append(sb1).toString();
        }
        int rows = len%(2*(numRows-1))==0?len/(2*(numRows-1)):1+len/(2*(numRows-1));
        StringBuffer sb = new StringBuffer();
        for(int i = 0;i<numRows;i++){
            if(i==0||i==(numRows-1)){
                for(int j = 0;j<rows;j++){
                    if(2*(numRows-1)*j+i<len)sb.append(s.charAt((numRows+1)*j+i));
                }
            }else{
                for(int j = 0;j<rows;j++){
                    if(2*(numRows-1)*j+i<len)sb.append(s.charAt(2*(numRows-1)*j+i));
                    if(2*(numRows-1)*(j+1)-i<len)sb.append(s.charAt(2*(numRows-1)*(j+1)-i));
                }
            }
        }
        return sb.toString();
        
    }
    
}