https://adventofcode.com/2020/day/2

password_checker.go

package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
)

func main() {
	sf, _ := os.Open("./input.txt")
	scanner := bufio.NewScanner(sf)

	count := 0

	for scanner.Scan() {
		if isValid(scanner.Text()) {
			count++
		}
	}

	println(count)
}

func isValid(entry string) bool {
	policy, password := split(entry, ": ")
	times, char := split(policy, " ")
	least, most := split(times, "-")

	count := strings.Count(password, char)
	leastCount, _ := strconv.Atoi(least)
	mostCount, _ := strconv.Atoi(most)

	return leastCount <= count && count <= mostCount
}

func split(str, sep string) (string, string) {
	split := strings.Split(str, sep)
	return split[0], split[1]

}

password_checker2.go

package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
)

func main() {
	sf, _ := os.Open("./input.txt")
	scanner := bufio.NewScanner(sf)

	count := 0

	for scanner.Scan() {
		if isValid(scanner.Text()) {
			count++
		}
	}

	println(count)
}

func isValid(entry string) bool {
	policy, password := split(entry, ": ")
	times, char := split(policy, " ")
	first, second := split(times, "-")

	p1, _ := strconv.Atoi(first)
	p2, _ := strconv.Atoi(second)

	p1c := password[p1-1:p1] == char
	p2c := password[p2-1:p2] == char
	return (p1c || p2c) && !(p1c && p2c)
}

func split(str, sep string) (string, string) {
	split := strings.Split(str, sep)
	return split[0], split[1]
}