feat: day 07 part 2 solution

Author: agrmohit

2024/07/main.go

@@ -4,6 +4,7 @@ import (
 	_ "embed"
 	"fmt"
 	"log"
+	"strconv"
 	"strings"
 
 	"github.com/agrmohit/aoc/internal/inputs"
@@ -12,6 +13,12 @@ import (
 //go:embed input.txt
 var input string
 
+func concat(a int, b int) int {
+	result, _ := strconv.Atoi(strconv.Itoa(a) + strconv.Itoa(b))
+
+	return result
+}
+
 // doesSolutionExist checks whether a solution exists recursively
 func doesSolutionExist(result int, current int, rest []int) bool {
 	// Exit condition
@@ -25,6 +32,19 @@ func doesSolutionExist(result int, current int, rest []int) bool {
 	return doesSolutionExist(result, current+current1, rest1) || doesSolutionExist(result, current*current1, rest1)
 }
 
+// doesSolutionExist checks whether a solution exists recursively, including concat operator
+func doesSolutionExist2(result int, current int, rest []int) bool {
+	// Exit condition
+	if len(rest) == 0 {
+		return result == current
+	}
+
+	current1 := rest[0]
+	rest1 := rest[1:]
+
+	return doesSolutionExist2(result, current+current1, rest1) || doesSolutionExist2(result, current*current1, rest1) || doesSolutionExist2(result, concat(current, current1), rest1)
+}
+
 func solvePart1(input string) int {
 	input = strings.ReplaceAll(input, ":", "")
 	rows, err := inputs.ExtractIntRows(input)
@@ -43,8 +63,28 @@ func solvePart1(input string) int {
 	return solutionExistsSum
 }
 
+func solvePart2(input string) int {
+	input = strings.ReplaceAll(input, ":", "")
+	rows, err := inputs.ExtractIntRows(input)
+	if err != nil {
+		log.Fatalf("ERROR: %v", err)
+	}
+
+	solutionExistsSum := 0
+
+	for _, line := range rows {
+		if doesSolutionExist2(line[0], line[1], line[2:]) {
+			solutionExistsSum += line[0]
+		}
+	}
+
+	return solutionExistsSum
+}
+
 func main() {
 	part1Solution := solvePart1(input)
+	part2Solution := solvePart2(input)
 
 	fmt.Println("Day 07 Part 1 solution:", part1Solution)
+	fmt.Println("Day 07 Part 2 solution:", part2Solution)
 }

2024/07/main_test.go

@@ -17,4 +17,13 @@ func TestSolution(t *testing.T) {
 			t.Errorf("Incorrect solution, got %d want %d", got, want)
 		}
 	})
+
+	t.Run("Day 07 part 2 test 1", func(t *testing.T) {
+		want := 11387
+		got := solvePart2(test1)
+
+		if got != want {
+			t.Errorf("Incorrect solution, got %d want %d", got, want)
+		}
+	})
 }