aoc-d1.go

package main

import (
	"bufio"
	"fmt"
	"strings"
	"time"
)

type Pair struct {
	s string
	n int
}

const (
	minLen = 3
	maxLen = 5
)

var pairs = [][]Pair{
	nil,
	nil,
	nil,
	{
		{"one", 1},
		{"six", 6},
		{"two", 2},
	},
	{
		{"five", 5},
		{"four", 4},
		{"nine", 9},
	},
	{
		{"eight", 8},
		{"seven", 7},
		{"three", 3},
	},
}

var pairs10 = [][]Pair{
	nil,
	nil,
	nil,
	{
		{"one", 10},
		{"six", 60},
		{"two", 20},
	},
	{
		{"five", 50},
		{"four", 40},
		{"nine", 90},
	},
	{
		{"eight", 80},
		{"seven", 70},
		{"three", 30},
	},
}

func main() {
	start := time.Now()
	sc := bufio.NewScanner(strings.NewReader(input))
	n := 0
	for sc.Scan() {
		x := scanDigit(sc.Text())
		n += x
	}
	used := time.Since(start)
	fmt.Println(n)
	fmt.Println("used:", used.String())
}

var digits = [256]int{
	'1': 1,
	'2': 2,
	'3': 3,
	'4': 4,
	'5': 5,
	'6': 6,
	'7': 7,
	'8': 8,
	'9': 9,
}

var digits10 = [256]int{
	'1': 10,
	'2': 20,
	'3': 30,
	'4': 40,
	'5': 50,
	'6': 60,
	'7': 70,
	'8': 80,
	'9': 90,
}

func scanDigit(s string) (n int) {
	leng := len(s)
	i := 0
	for i <= minLen {
		c := s[i]
		if x := digits10[c]; x != 0 {
			n = x
			goto E
		}
		i++
		for j := 0; j + minLen <= i; j++ {
			ss := s[j:i]
			for _, p := range pairs10[len(ss)] {
				if ss == p.s {
					n = p.n
					goto E
				}
			}
		}
	}
	for i < leng {
		c := s[i]
		if x := digits10[c]; x != 0 {
			n = x
			goto E
		}
		i++
		for j := i - maxLen; j + minLen <= i; j++ {
			ss := s[j:i]
			for _, p := range pairs10[len(ss)] {
				if ss == p.s {
					n = p.n
					goto E
				}
			}
		}
	}
	E:
	r := leng - maxLen
	i = leng
	for i > r {
		i--
		c := s[i]
		if x := digits[c]; x != 0  {
			n += x
			goto F
		}
		for j := i + minLen; j <= leng; j++ {
			ss := s[i:j]
			for _, p := range pairs[len(ss)] {
				if ss == p.s {
					n += p.n
					goto F
				}
			}
		}
	}
	for i >= 0 {
		i--
		c := s[i]
		if x := digits[c]; x != 0  {
			n += x
			goto F
		}
		for j := minLen; j <= maxLen; j++ {
			ss := s[i:i + j]
			for _, p := range pairs[len(ss)] {
				if ss == p.s {
					n += p.n
					goto F
				}
			}
		}
	}
F:
	return
}

const input = `two1nine
eightwothree
abcone2threexyz
xtwone3four
4nineeightseven2
zoneight234
7pqrstsixteen`