5p1.txt

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
)

func makeJumpsList(filepath string) ([]int, error) {
	f, err := os.Open(filepath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	jumps := []int{}
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		s := scanner.Text()
		if s == "" {
			continue
		}
		i, err := strconv.Atoi(s)
		if err != nil {
			return nil, err
		}
		jumps = append(jumps, i)
	}
	return jumps, nil
}

func main() {
	jumps, err := makeJumpsList("input")
	if err != nil {
		log.Fatal(err)
	}

	var (
		count  = 0
		end    = len(jumps) - 1
		i      = 0
		offset = 0
	)
	for i <= end {
		offset = jumps[i]
		if offset >= 3 {
			jumps[i]--
		} else {
			jumps[i]++
		}
		i += offset
		count++
	}

	fmt.Println(count)
}