package string;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

/**

* Created by gouthamvidyapradhan on 19/05/2017.

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".

*/

public class ZigZagConversion

{

/**

* Main method

* @param args

*/

public static void main(String[] args)

{

System.out.println(new ZigZagConversion().convert("PAYPALISHIRING", 5));

}

/**

* Convert and return the result

* @param s input string

* @param numRows max rows

* @return Result string

*/

public String convert(String s, int numRows) {

if(s == null || s.length() <= numRows || numRows == 1) return s;

List<String> list = new ArrayList<>();

char[] A = new char[numRows];

int direction = 1; // 1 indicates forward, 0 indicates backwards

int n = 1;

A[0] = s.charAt(0);

for(int j = 1; j < numRows;) {

if(n >= s.length()) break;

A[j] = s.charAt(n++);

if(j == numRows - 1) {

list.add(String.valueOf(A));

A = new char[numRows];

Arrays.fill(A, ' ');

direction = 0;

}

else if(j == 0) {

list.add(String.valueOf(A));

A = new char[numRows];

Arrays.fill(A, ' ');

direction = 1;

}

j = direction == 1 ? j + 1 : j - 1;

}

if(!String.valueOf(A).trim().isEmpty())

list.add(String.valueOf(A));

char[] arr = new char[s.length()];

int k = 0;

for(int j = 0; j < numRows; j ++) {

for (String aList : list) {

if (aList.charAt(j) != ' ')

arr[k++] = aList.charAt(j);

}

}

return new String(arr).trim();

}

}