Day01

Day01/optimized.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"sort"
+)
+
+func optimized() {
+	// Read the file in one step
+	content, err := os.ReadFile("./input.json")
+	if err != nil {
+		log.Fatalf("Error when opening input.json: %v", err)
+	}
+
+	// Parse the JSON
+	var payload struct {
+		ListA []int `json:"list_a"`
+		ListB []int `json:"list_b"`
+	}
+	if err := json.Unmarshal(content, &payload); err != nil {
+		log.Fatalf("Error when unmarshalling input.json: %v", err)
+	}
+
+	// Part 1: Calculate the sum of absolute differences between sorted lists
+	sort.Ints(payload.ListA)
+	sort.Ints(payload.ListB)
+
+	sumPart1 := 0
+	for i := range payload.ListA {
+		sumPart1 += abs(payload.ListA[i] - payload.ListB[i])
+	}
+	fmt.Printf("Sum of Part 1: %d\n", sumPart1)
+
+	// Part 2: Calculate weighted sum of common elements
+	sumPart2 := 0
+	countMap := make(map[int]int)
+	for _, v := range payload.ListB {
+		countMap[v]++
+	}
+
+	for _, v := range payload.ListA {
+		if countMap[v] > 0 {
+			sumPart2 += v * countMap[v]
+			countMap[v] = 0 // Avoid double-counting
+		}
+	}
+	fmt.Printf("Sum of Part 2: %d\n", sumPart2)
+}
+
+// Helper function for absolute value
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}