days

2024/go/day07/day07.go

@@ -0,0 +1,140 @@
+package day07
+
+import (
+	"adventofcode2024/utils"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type Op int
+
+const (
+	Add Op = iota
+	Mul
+	Conc
+)
+
+func Part1(input string) int {
+	val := 0
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		parts := strings.Split(line, ":")
+		result := utils.MustAtoi(parts[0])
+		numStrings := strings.Fields(parts[1])
+		var numbers []int
+		for _, numStr := range numStrings {
+			num := utils.MustAtoi(numStr)
+			numbers = append(numbers, num)
+		}
+		bitmask := 1 << (len(numbers) - 1)
+		for i := 0; i < bitmask; i++ {
+			calc := 0
+			switch isNthBitSet(i, 0) {
+			case true:
+				calc = numbers[0] + numbers[1]
+			case false:
+				calc = numbers[0] * numbers[1]
+			}
+
+			for n := 1; n < len(numbers)-1; n++ {
+				switch isNthBitSet(i, n) {
+				case true:
+					calc = calc + numbers[n+1]
+				case false:
+					calc = calc * numbers[n+1]
+				}
+			}
+			if calc == result {
+				fmt.Printf("result: %v numbers:%v  count: %d\n", result, numbers, bitmask)
+				val += result
+				break
+			}
+		}
+	}
+	return val
+}
+
+func Part2(input string) int {
+	val := 0
+	lines := strings.Split(input, "\n")
+	for _, line := range lines {
+		parts := strings.Split(line, ":")
+		result := utils.MustAtoi(parts[0])
+		numStrings := strings.Fields(parts[1])
+		var numbers []int
+		for _, numStr := range numStrings {
+			num := utils.MustAtoi(numStr)
+			numbers = append(numbers, num)
+		}
+		operations := []Op{Add, Mul, Conc}
+		results := [][]Op{}
+		generatePermutations(operations, len(numbers)-1, []Op{}, &results)
+		for _, op := range results {
+			calc := 0
+			switch op[0] {
+			case Add:
+				calc = numbers[0] + numbers[1]
+			case Mul:
+				calc = numbers[0] * numbers[1]
+			case Conc:
+				calc = concat(numbers[0], numbers[1])
+			}
+
+			for n := 1; n < len(numbers)-1; n++ {
+				switch op[n] {
+				case Add:
+					calc = calc + numbers[n+1]
+				case Mul:
+					calc = calc * numbers[n+1]
+				case Conc:
+					calc = concat(calc, numbers[n+1])
+				}
+			}
+			if calc == result {
+				fmt.Printf("result: %v numbers:%v\n", result, numbers)
+				val += result
+				break
+			}
+		}
+	}
+	return val
+}
+
+func isNthBitSet(num, n int) bool {
+	return num&(1<<n) != 0
+}
+
+func getOp(row, col int) Op {
+	vals := []Op{Add, Mul, Conc}
+	// Column 0 cycles as row / 3
+	if col == 0 {
+		return vals[row/3]
+	}
+	// Column 1 cycles as row % 3
+	return vals[row%3]
+}
+
+// Recursive function to generate permutations
+func generatePermutations(ops []Op, n int, prefix []Op, results *[][]Op) {
+	if n == 0 {
+		// Append a copy of the current prefix to the results
+		*results = append(*results, append([]Op{}, prefix...))
+		return
+	}
+
+	// Iterate over all operations and build the combinations
+	for _, op := range ops {
+		generatePermutations(ops, n-1, append(prefix, op), results)
+	}
+}
+
+func concat(a, b int) int {
+	aStr := strconv.Itoa(a)
+	bStr := strconv.Itoa(b)
+
+	concatStr := aStr + bStr
+
+	result, _ := strconv.Atoi(concatStr)
+	return result
+}