6. Zigzag Conversion

Posted on | In |
  • Source : Link
  • Author : Han
  • Date : 2022-01-17

Problems

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)

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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:

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string convert(string s, int numRows);

Example 1:

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Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

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Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I

Solution

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class Solution {
    fun convert(s: String, numRows: Int): String {
        val rows = Array(numRows) { StringBuilder() }
        val zigzagLength = maxOf(1, 2 * (numRows - 1))

        s.indices.forEach { i ->
            val current = i % zigzagLength
            val row = when {
                current < numRows -> current
                else -> zigzagLength - current
            }
            rows[row].append(s[i])
        }

        return rows.joinToString("")
    }
}