feat: day 02 part 2 solution

Author: agrmohit

2024/02/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	_ "embed"
 	"fmt"
+	"slices"
 
 	"github.com/agrmohit/advent-of-code/internal/inputs"
 	mathinternal "github.com/agrmohit/advent-of-code/internal/math"
@@ -11,6 +12,30 @@ import (
 //go:embed input.txt
 var input string
 
+// checkIsSafe takes an int row and returns whether it is safe
+func checkIsSafe(row []int) bool {
+	isIncreasing := row[1] > row[0]
+
+	for i := 1; i < len(row); i++ {
+		// If 2 consecutive numbers are same, it's unsafe
+		if row[i] == row[i-1] {
+			return false
+		}
+
+		// If `isIncreasing` flips anytime during execution, it's unsafe
+		if isIncreasing != (row[i] > row[i-1]) {
+			return false
+		}
+
+		// If absolute difference between consecutive numbers is not 1, 2 or 3
+		if mathinternal.Abs(row[i]-row[i-1]) > 3 {
+			return false
+		}
+	}
+
+	return true
+}
+
 func solvePart1(input string) int {
 	rows, err := inputs.ExtractIntRows(input)
 	if err != nil {
@@ -20,31 +45,34 @@ func solvePart1(input string) int {
 	safeCount := 0
 
 	for _, row := range rows {
-		isSafe := true
-		isIncreasing := row[1] > row[0]
-
-		for i := 1; i < len(row); i++ {
-			// If 2 consecutive numbers are same, it's unsafe
-			if row[i] == row[i-1] {
-				isSafe = false
-				break
-			}
+		if checkIsSafe(row) {
+			safeCount++
+		}
+	}
 
-			// If `isIncreasing` flips anytime during execution, it's unsafe
-			if isIncreasing != (row[i] > row[i-1]) {
-				isSafe = false
-				break
-			}
+	return safeCount
+}
 
-			// If absolute difference between consecutive numbers is not 1, 2 or 3
-			if mathinternal.Abs(row[i]-row[i-1]) > 3 {
-				isSafe = false
-				break
-			}
-		}
+func solvePart2(input string) int {
+	rows, err := inputs.ExtractIntRows(input)
+	if err != nil {
+		panic(err)
+	}
+
+	safeCount := 0
 
-		if isSafe {
+	for _, row := range rows {
+		// Check whether it is safe without removing any element
+		if checkIsSafe(row) {
 			safeCount++
+		} else {
+			// Remove each element one by one and check whether it is safe
+			for i := range row {
+				if checkIsSafe(slices.Concat(row[:i], row[i+1:])) {
+					safeCount++
+					break
+				}
+			}
 		}
 	}
 
@@ -53,6 +81,8 @@ func solvePart1(input string) int {
 
 func main() {
 	part1Solution := solvePart1(input)
+	part2Solution := solvePart2(input)
 
-	fmt.Println("Day 02 Part 1 solution:", part1Solution)
+	fmt.Println("Day 01 Part 1 solution:", part1Solution)
+	fmt.Println("Day 01 Part 2 solution:", part2Solution)
 }

2024/02/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 02 part 2", func(t *testing.T) {
+		want := 4
+		got := solvePart2(test1)
+
+		if got != want {
+			t.Errorf("Incorrect solution, got %d want %d", got, want)
+		}
+	})
 }