zigzag-conversion main.go

package main

import (
	"fmt"
	"strings"
)

func convert(s string, numRows int) string {
	length := int(len(s))

	if numRows == 1 {
		return s
	}

	t := strings.Split(s, "")
	res := make([]string, length)
	numDiv := numRows - 1
	i, j, y := 0, 0, 0

	landmark := make([]int, 0)
	belowLandmark := make([]int, 0)

	isAbove := true
	for i = 0; i <= length-1; i++ {
		if i%numDiv == 0 {
			if isAbove {
				res[j] = t[i]
				j++
				landmark = append(landmark, i)
				isAbove = false
			} else {
				belowLandmark = append(belowLandmark, i)
				isAbove = true
			}
		}
	}

	maxRun := numRows - 1
	k := 0

	for i = 1; i <= maxRun; i++ {
		for y = 0; y <= len(landmark)-1; y++ {
			beforeIndex := landmark[y] - i
			afterIndex := landmark[y] + i
			if beforeIndex >= 0 && beforeIndex <= length-1 {
				res[j] = t[beforeIndex]
				j++
			}

			if k >= 0 && k <= int(len(belowLandmark))-1 && belowLandmark[k] == afterIndex {
				k++
			} else {
				if afterIndex >= 0 && afterIndex <= length-1 {
					res[j] = t[afterIndex]
					j++
				}
			}
		}
	}

	return strings.Join(res, "")
}

func main() {
	s := "PAYPALISHIRING"
	n := 3
	res := convert(s, n)
	fmt.Println("res:", res)
}