Complete Day 2 part 2

Author: nkdem

2024/day2/day2.go

@@ -8,7 +8,46 @@ import (
 	"strings"
 )
 
+func RemoveIndex(s []int, index int) []int {
+	new_s := []int{}
+	for i, v := range s {
+		if i != index {
+			new_s = append(new_s, v)
+		}
+	}
+	return new_s
+}
+
+func pop(slice []int) (int, []int) {
+	return slice[0], slice[1:]
+}
+
+func isSafeRow(row []int) bool {
+	prev := row[0]
+	curr := row[1]
+	increasing := true
+	if prev > curr {
+		increasing = false
+	}
+	for j := 1; j < len(row); j++ {
+		curr = row[j]
+		diff := int(math.Abs(float64(prev - curr)))
+		if !(diff >= 1 && diff <= 3) {
+			return false
+		}
+		if increasing && prev > curr {
+			return false
+		}
+		if !increasing && prev < curr {
+			return false
+		}
+		prev = curr
+	}
+	return true
+}
+
 func main() {
+	// fi, err := os.Open("day2_sample")
 	fi, err := os.Open("day2_input")
 	if err != nil {
 		panic(err)
@@ -29,39 +68,54 @@ func main() {
 		}
 		list = append(list, row)
 	}
-	fmt.Println(list)
 
-	candidates := [][]int{}
-	for _, row := range list {
-		prev := row[0]
-		curr := row[1]
-		increasing := true
-		if prev > curr {
-			increasing = false
+	candidates := make(map[int]bool)
+	for i, row := range list {
+		candidates[i] = isSafeRow(row)
+	}
+	partA := 0
+	for _, v := range candidates {
+		if v {
+			partA++
 		}
-		finished := true
-		for i := 1; i < len(row); i++ {
-			curr = row[i]
-			diff := int(math.Abs(float64(prev - curr)))
-			if !(diff >= 1 && diff <= 3) {
-				finished = false
-				break
-			}
-			if increasing && prev > curr {
-				finished = false
-				break
-			}
-			if !increasing && prev < curr {
-				finished = false
+	}
+
+	fmt.Println(partA)
+
+	// brute force approach for b
+	// 1. get all unsafe indexes (false)
+	// 2. for each unsafe row, remove first element and check if it is safe, second element, and so on, if at least one is safe, then it is safe
+	// and we can remove it from the unsafe list
+	unsafe := []int{}
+	for i, v := range candidates {
+		if !v {
+			unsafe = append(unsafe, i)
+		}
+	}
+
+	for len(unsafe) > 0 {
+		i, rest := pop(unsafe)
+		unsafe = rest
+		row := list[i]
+		n := len(row)
+		for j := 0; j < n; j++ {
+			new_row := RemoveIndex(row, j)
+
+			fmt.Println(new_row)
+			if isSafeRow(new_row) {
+				fmt.Println("safe")
+				candidates[i] = true
 				break
 			}
-			prev = curr
 		}
-		if finished {
-			candidates = append(candidates, row)
+	}
+
+	partB := 0
+	for _, v := range candidates {
+		if v {
+			partB++
 		}
 	}
-	fmt.Println(len(candidates))
+	fmt.Println(partB)
 
-	// sort the
 }