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package main
import (
"fmt"
"os"
"strconv"
"strings"
)
func FileRead(path string) string {
file, err := os.ReadFile(path)
if err != nil {
fmt.Println("Couldn't Read file: ", err)
}
return string(file)
}
type Op = string
const (
Plus Op = "+"
Mul Op = "*"
Concat Op = "||"
)
var OpsOne = []Op{Plus, Mul}
var OpsTwo = []Op{Plus, Mul, Concat}
type Calibration struct {
target int
vals []int
}
type Expression = []string
func (c Calibration) String() string {
valsStr := strings.Trim(strings.Join(strings.Fields(fmt.Sprint(c.vals)), ", "), "[]")
return fmt.Sprintf("Calibration(target: %d, vals: [%s])", c.target, valsStr)
}
func parseInput(data string) []Calibration {
lines := strings.Split(data, "\n")
var cals []Calibration
for _, line := range lines {
if len(line) > 0 {
cal := strings.Split(line, ": ")
target, _ := strconv.Atoi(cal[0])
var vals []int
for _, num := range strings.Split(cal[1], " ") {
val, _ := strconv.Atoi(num)
vals = append(vals, val)
}
calibration := Calibration{
target: target,
vals: vals,
}
cals = append(cals, calibration)
}
}
return cals
}
func generatePossibleExpressions(opsLeft int, expr *Expression, expressions *[]Expression, Ops []string) {
if opsLeft == 0 {
comb := make([]string, len(*expr))
copy(comb, *expr)
*expressions = append(*expressions, comb)
} else {
for _, op := range Ops {
// choose
*expr = append(*expr, op)
// explore
generatePossibleExpressions(opsLeft-1, expr, expressions, Ops)
// unchoose
*expr = (*expr)[:len(*expr)-1]
}
}
}
func removeElement(s []int, i int) ([]int, error) {
if i >= len(s) || i < 0 {
return nil, fmt.Errorf("Index is out of range. Index is %d with slice length %d", i, len(s))
}
return append(s[:i], s[i+1:]...), nil
}
func removeElementString(s []string, i int) ([]string, error) {
if i >= len(s) || i < 0 {
return nil, fmt.Errorf("Index is out of range. Index is %d with slice length %d", i, len(s))
}
return append(s[:i], s[i+1:]...), nil
}
func evalPartOne(vals []int, expression *Expression) int {
for _, op := range *expression {
left := vals[0]
right := vals[1]
if op == Mul {
vals, _ = removeElement(vals, 0)
vals[0] = left * right
} else if op == Plus {
vals, _ = removeElement(vals, 0)
vals[0] = left + right
}
}
return vals[0]
}
func evalPartTwo(vals []int, expression *Expression) int {
for _, op := range *expression {
left := vals[0]
right := vals[1]
if op == Mul {
vals, _ = removeElement(vals, 0)
vals[0] = left * right
} else if op == Plus {
vals, _ = removeElement(vals, 0)
vals[0] = left + right
} else if op == "||" {
vals, _ = removeElement(vals, 0)
// vals[0], _ = strconv.Atoi(strconv.Itoa(left) + strconv.Itoa(right))
multiplier := 1
for temp := right; temp > 0; temp /= 10 {
multiplier *= 10
}
vals[0] = left*multiplier + right
}
}
// fmt.Printf("expression: %v\n", (*expression))
// fmt.Printf("vals: %v\n", vals)
return vals[0]
}
func solve_part_one(data string) int64 {
calibrations := parseInput(data)
var ans int64 = 0
for _, calibration := range calibrations {
var expressions []Expression
generatePossibleExpressions((len(calibration.vals) - 1), &[]string{}, &expressions, OpsOne)
for _, expr := range expressions {
copy_vals := make([]int, len(calibration.vals))
copy(copy_vals, calibration.vals)
if evalPartOne(copy_vals, &expr) == calibration.target {
// fmt.Printf("expr: %v\n", expr)
ans += int64(calibration.target)
break
}
}
// fmt.Printf("expressions: %v\n", expressions)
expressions = []Expression{}
}
return ans
}
func solve_part_two(data string) int64 {
calibrations := parseInput(data)
var ans int64 = 0
for _, calibration := range calibrations {
var expressions []Expression
generatePossibleExpressions((len(calibration.vals) - 1), &[]string{}, &expressions, OpsTwo)
for _, expr := range expressions {
copy_vals := make([]int, len(calibration.vals))
copy(copy_vals, calibration.vals)
if evalPartTwo(copy_vals, &expr) == calibration.target {
// fmt.Printf("expr: %v\n", expr)
ans += int64(calibration.target)
break
}
}
expressions = []Expression{}
}
return ans
}
func main() {
test := FileRead("../input/day07.test")
prod := FileRead("../input/day07.prod")
fmt.Println("Part_1 test: ", solve_part_one(test))
fmt.Println("Part_1 prod: ", solve_part_one(prod))
fmt.Println("Part_2 test: ", solve_part_two(test))
fmt.Println("Part_2 prod: ", solve_part_two(prod))
}
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