adventofcode/2017/day01/day01.go

package main

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

func main() {
	inp := StdinToString()
	part1(inp)
	part2(inp)
}

func part1(inp string) {
	sum := 0
	for k := range inp {
		tstIdx := getCompareIndex(k, 1, len(inp))
		sum += getCompareResult(inp[k], inp[tstIdx])
	}
	fmt.Println("Part 1:", sum)
}

func part2(inp string) {
	sum := 0
	for k := range inp {
		tstIdx := getCompareIndex(k, (len(inp) / 2), len(inp))
		sum += getCompareResult(inp[k], inp[tstIdx])
	}
	fmt.Println("Part 2:", sum)
}

func getCompareIndex(curr, add, max int) int {
	return int(math.Mod(float64(curr+add), float64(max)))
}

func getCompareResult(c1, c2 byte) int {
	if c1 != c2 {
		return 0
	}
	return Atoi(string(c1))
}

func StdinToString() string {
	var input string
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		input += scanner.Text()
	}
	return input
}

func Atoi(i string) int {
	var ret int
	var err error
	if ret, err = strconv.Atoi(i); err != nil {
		log.Fatal("Invalid Atoi")
	}
	return ret
}