Advent of Code 2021 Day 7

7a.go

package main

import (
	_ "embed"
	"fmt"
	"math"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

func parseInt(val string) int {
	v, err := strconv.Atoi(val)
	if err != nil {
		panic(err)
	}
	return v
}

func calcFuel(target int, dists []int) int {
	fuel := 0
	for _, dist := range dists {
		fuel += int(math.Abs(float64(dist - target)))
	}
	return fuel
}

func main() {
	vs := strings.Split(input, ",")
	nums := make([]int, len(vs))
	for i, v := range vs {
		nums[i] = parseInt(v)
	}

	min := 100
	max := -1
	for _, v := range nums {
		if v < min {
			min = v
		}
		if v > max {
			max = v
		}
	}

	lowest := 100000000
	for v := min; v <= max; v++ {
		fuel := calcFuel(v, nums)
		if fuel < lowest {
			lowest = fuel
		}
	}
	fmt.Println(lowest)
}

7b.go

package main

import (
	_ "embed"
	"fmt"
	"math"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

func parseInt(val string) int {
	v, err := strconv.Atoi(val)
	if err != nil {
		panic(err)
	}
	return v
}

func calcNum(v int) int {
	/*	diff := 0
		for i := 1; i <= v; i++ {
			diff += i
		}
		return diff*/
	return v * (v + 1) / 2
}

func calcFuel(target int, dists []int) int {
	fuel := 0
	for _, dist := range dists {
		d := int(math.Abs(float64(dist - target)))
		diff := calcNum(d)
		fuel += diff
	}
	return fuel
}

func main() {
	vs := strings.Split(input, ",")
	nums := make([]int, len(vs))
	for i, v := range vs {
		nums[i] = parseInt(v)
	}

	min := 100
	max := -1
	for _, v := range nums {
		if v < min {
			min = v
		}
		if v > max {
			max = v
		}
	}

	lowest := math.MaxInt
	for v := min; v <= max; v++ {
		fuel := calcFuel(v, nums)
		if fuel < lowest {
			lowest = fuel
		}
	}
	fmt.Println(lowest)
}