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6. Zigzag Conversion

Medium

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 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

Example 3:

Input: s = “A”, numRows = 1

Output: “A”

Constraints:

• 1 <= s.length <= 1000
• s consists of English letters (lower-case and upper-case), ',' and '.'.
• 1 <= numRows <= 1000

Solution

import scala.collection.mutable

object Solution {
    def convert(s: String, numRows: Int): String = {
        if (numRows == 1) return s
        val map = new mutable.HashMap[Int, String]()
        var string = ""
        var counter = 0
        var counterBool = true
        for (i <- s) {
            val currentValue = map.getOrElse(counter, "")
            map(counter) = currentValue + i.toString
            counterBool = if (counter == numRows - 1) false else if (counter == 0) true else counterBool
            counter = if (counterBool) counter + 1 else counter - 1
        }
        map.foreach {
            case (_, value) => string += value
        }
        string
    }
}

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