feat(2020-15/angch): ez

Author: angch

2020-15/angch/input.txt

@@ -0,0 +1 @@
+12,20,0,6,1,17,7

2020-15/angch/main.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"bufio"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func do(fileName string) (int, int) {
+	ret1, ret2 := 0, 0
+
+	file, err := os.Open(fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+
+	nums := make(map[int][]int)
+	last := 0
+	pos := 0
+	for scanner.Scan() {
+		l := scanner.Text()
+		a := strings.Split(l, ",")
+		for k, v := range a {
+			num, _ := strconv.Atoi(v)
+			_, ok := nums[num]
+			if !ok {
+				nums[num] = make([]int, 0, 2)
+			}
+			nums[num] = append(nums[num], k+1)
+			pos = k + 1
+			last = num
+		}
+	}
+
+	out := 0
+	for {
+		if len(nums[last]) == 1 {
+			out = 0
+		} else {
+			out = nums[last][len(nums[last])-1] - nums[last][len(nums[last])-2]
+		}
+		pos++
+
+		_, ok := nums[out]
+		if !ok {
+			nums[out] = make([]int, 0, 2)
+		}
+		if len(nums[out]) <= 1 {
+			nums[out] = append(nums[out], pos)
+		} else {
+			nums[out][0] = nums[out][1]
+			nums[out][1] = pos
+		}
+		last = out
+		if pos == 2020 {
+			ret1 = last
+		}
+		if pos >= 30000000 {
+			// if pos >= 2020 {
+			break
+		}
+	}
+	ret2 = last
+
+	return ret1, ret2
+}
+
+func main() {
+	log.Println(do("test.txt"))
+	// log.Println(do("test2.txt"))
+	log.Println(do("input.txt"))
+}