6. Zigzag Conversion

Medium
String

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
func convert(s string, numRows int) string {
	rows := make([][]string, numRows)
	for i := range rows {
		rows[i] = make([]string, len(s))
	}

	x := 0
	y := 0

	dx := []int{1, -1}
	dy := []int{0, 1}
	d := 0

	for _, c := range s {
		rows[x][y] = string(c)
		if x == numRows-1 {
			d = 1
		} else if x == 0 {
			d = 0
		}
		x += dx[d]
        x = max(x, 0)
		y += dy[d]
	}

	result := ""
	for _, row := range rows {
		for _, c := range row {
			if c != "" {
				result += c
			}
		}
	}

	return result
}