feat: 2024 day 1

2024/1/1.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func p1(data []string) int {
+	var left, right []int
+	var totalDistance int
+
+	for i := 0; i < len(data); i++ {
+		splitData := strings.Split(data[i], "   ")
+		splitInt, err := sliceAtoi(splitData)
+		if err != nil {
+			fmt.Println(err)
+			return -1
+		}
+		
+		left = append(left, splitInt[0])
+		right = append(right, splitInt[1])
+	}
+
+	// sort
+	sort.Ints(left[:])
+	sort.Ints(right[:])
+
+	// continue looping by the data length
+	for i := 0; i < len(data); i++ {
+		modLeft, smallestLeft := remove(left, 0)
+		modRight, smallestRight := remove(right, 0)
+
+		left = modLeft
+		right = modRight
+
+		// idk why it has to use float64 with such a probably small number but i dont care
+		totalDistance += int(math.Abs(float64(smallestLeft - smallestRight)))
+	}
+
+	return totalDistance
+}
+
+func p2(data []string) int {
+	var left, right []int
+	var totalSimilarity int
+
+	for i := 0; i < len(data); i++ {
+		splitData := strings.Split(data[i], "   ")
+		splitInt, err := sliceAtoi(splitData)
+		if err != nil {
+			fmt.Println(err)
+			return -1
+		}
+		
+		left = append(left, splitInt[0])
+		right = append(right, splitInt[1])
+	}
+
+	// sort
+	sort.Ints(left[:])
+	sort.Ints(right[:])
+
+	// here comes the funny
+	occurence := frequencyMap(right)
+	for i := 0; i < len(left); i++ {
+		currentOcc := left[i]
+		countOcc := occurence[currentOcc]
+
+		totalSimilarity += currentOcc * countOcc
+	}
+
+	return totalSimilarity
+}
+
+func main() {
+	data, err := os.ReadFile("input.txt")
+	if err != nil {
+		fmt.Println("File reading error", err)
+		return
+	}
+	lines := strings.Split(string(data), "\n")
+
+	fmt.Println("Part 1:", p1(lines))
+	fmt.Println("Part 2:", p2(lines))
+}
+
+// HELPER FUNCTIONS
+
+// https://stackoverflow.com/a/24973180
+func sliceAtoi(sa []string) ([]int, error) {
+    si := make([]int, 0, len(sa))
+    for _, a := range sa {
+        i, err := strconv.Atoi(a)
+        if err != nil {
+            return si, err
+        }
+        si = append(si, i)
+    }
+    return si, nil
+}
+
+// modified from https://stackoverflow.com/a/37335777
+func remove(slice []int, s int) ([]int, int) {
+    removedElement := slice[s]
+    newSlice := append(slice[:s], slice[s+1:]...)
+    return newSlice, removedElement
+}
+
+// https://www.geeksforgeeks.org/golang-program-to-find-the-frequency-of-each-element-in-an-array/
+func frequencyMap(arr []int) map[int]int {
+    freq := make(map[int]int)
+    for _ , num :=  range arr {
+        freq[num] = freq[num]+1
+    }
+    return freq
+}