> For the complete documentation index, see [llms.txt](https://blog.bernardw.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://blog.bernardw.com/problems/zigzag-conversion.md).

# 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"
<br>
<br>Write the code that will take a string and make this conversion given a number of rows:

> convert("PAYPALISHIRING", 3) 

should return 

> "PAHNAPLSIIGYIR"
```

{% tabs %}
{% tab title="Scala" %}

```scala
def convert(s: String, numRows: Int): String = {
  numRows match {
    case 1 => s
    case n if n > 1 => {
      val lengthPerCycle = 2 * numRows - 2
      val cycles = (s.length / lengthPerCycle) + 1
      val sb = new StringBuilder
      for (i <- 0 until numRows) {
        for (cycle <- 0 until cycles) {
          // print full vertical
          val col = (cycle * lengthPerCycle) + i
          if (col < s.length)
            sb.append(s(col))
          // print diagonal
          val dia = ((cycle + 1) * lengthPerCycle) - i
          if (i != 0 && i < numRows - 1 && dia < s.length)
            sb.append(s(dia))
        }
      }
      sb.toString()
    }
    case _ => throw new Error("negative number")
  }
}

convert("PAYPALISHIRING", 3)
```

{% endtab %}

{% tab title="Second Tab" %}

{% endtab %}
{% endtabs %}