aoc2020-02.go

package main

import (
	"fmt"
	"github.com/spellgen/scan"
	"os"
)

type passLine struct {
	s    int
	e    int
	ch   string
	list string
}

func (p passLine) Parse(in string) (scan.LineScanner, bool) {
	n, err := fmt.Sscanf(in, "%d-%d %s%s", &p.s, &p.e, &p.ch, &p.list)
	return p, n == 4 && err == nil
}

func main() {
	if len(os.Args) < 2 {
		panic("no args")
	}
	file := os.Args[1]
	fh, err := os.Open(file)
	if err != nil {
		panic(err)
	}
	data, err := scan.ReadAll(fh, passLine{})
	if err != nil {
		panic(err)
	}

	t1sum := 0
	t2sum := 0
	for _, p := range data {
		if test1(p.(passLine)) {
			t1sum++
		}
		if test2(p.(passLine)) {
			t2sum++
		}
	}

	fmt.Printf("test1=%d\n", t1sum)
	fmt.Printf("test2=%d\n", t2sum)
}

func test1(p passLine) bool {
	ch := p.ch[0]
	var n = 0
	for k := range p.list {
		if p.list[k]==ch {
			n++
		}
	}
	return n>=p.s && n<=p.e
}

func test2(p passLine) bool {
	ch := p.ch[0]
	count := 0
	if p.list[p.s-1]==ch {
		count++
	}
	if p.list[p.e-1]==ch {
		count++
	}
	return count==1
}