2018 day 18 Done

2018/day18/day18.go

@@ -0,0 +1,202 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"time"
+)
+
+const (
+	DIR_N  = -1i
+	DIR_NE = 1 - 1i
+	DIR_E  = 1
+	DIR_SE = 1 + 1i
+	DIR_S  = 1i
+	DIR_SW = -1 + 1i
+	DIR_W  = -1
+	DIR_NW = -1 - 1i
+
+	CLEAR_SCREEN = "\033[H\033[2J"
+)
+
+var scan []byte
+var next []byte
+var prevScans [][]byte
+var width, height int
+
+func main() {
+	stdinToByteSlice()
+	part1()
+	part2()
+}
+
+func part1() {
+	printScan()
+	for i := 0; i < 10; i++ {
+		fmt.Print(CLEAR_SCREEN)
+		scan = tickToNext()
+		printScan()
+		time.Sleep(time.Millisecond * 250)
+	}
+	var ttlOpen, ttlTrees, ttlLmbr int
+	for i := range scan {
+		switch getByte(getPosFromInt(i)) {
+		case '.':
+			ttlOpen++
+		case '|':
+			ttlTrees++
+		case '#':
+			ttlLmbr++
+		}
+	}
+	_ = ttlOpen
+	fmt.Println("= Part 1 =")
+	fmt.Println(ttlTrees * ttlLmbr)
+}
+
+// 191080?
+func part2() {
+	var isDupe bool
+	var i int
+	target := 1000000000
+	for i = 0; i < target; i++ {
+		//fmt.Print(CLEAR_SCREEN, target)
+		next := tickToNext()
+		if isDupe, prevScans = checkDuplicateState(next, prevScans); isDupe {
+			i++
+			scan = next
+			break
+		}
+		prevScans = append(prevScans, next)
+		scan = next
+	}
+	// We need to find the state after `target` increments
+	scan = prevScans[(target-i)%len(prevScans)]
+	var ttlOpen, ttlTrees, ttlLmbr int
+	for i := range scan {
+		switch getByte(getPosFromInt(i)) {
+		case '.':
+			ttlOpen++
+		case '|':
+			ttlTrees++
+		case '#':
+			ttlLmbr++
+		}
+	}
+	_ = ttlOpen
+	fmt.Println("= Part 2 =")
+	fmt.Println(ttlTrees * ttlLmbr)
+}
+
+// checkDuplicateState returns the slice of prev that has all remaining available states
+func checkDuplicateState(s []byte, prev [][]byte) (bool, [][]byte) {
+	for i, v := range prev {
+		if areasAreEqual(s, v) {
+			return true, prev[i:]
+		}
+	}
+	return false, prev
+}
+
+func areasAreEqual(a1, a2 []byte) bool {
+	for i := range a1 {
+		if a1[i] != a2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func tickToNext() []byte {
+	var ret []byte
+	for i := 0; i < len(scan); i++ {
+		c := getPosFromInt(i)
+		_, sTree, sLmbr := getSurroundingCounts(c)
+		b := getByte(c)
+		switch b {
+		case '.':
+			if sTree >= 3 {
+				ret = append(ret, '|')
+			} else {
+				ret = append(ret, '.')
+			}
+		case '|':
+			if sLmbr >= 3 {
+				ret = append(ret, '#')
+			} else {
+				ret = append(ret, '|')
+			}
+		case '#':
+			if sLmbr > 0 && sTree > 0 {
+				ret = append(ret, '#')
+			} else {
+				ret = append(ret, '.')
+			}
+		}
+	}
+	return ret
+}
+
+// getSurroundingCounts takes a pos and returns:
+//	Number of open areas
+//	Number of trees
+//  Number of lumberyards
+// Surrounding that spot
+func getSurroundingCounts(c complex64) (int, int, int) {
+	var sOpen, sTree, sLmbr int
+	for _, v := range []complex64{DIR_NW, DIR_N, DIR_NE, DIR_W, DIR_E, DIR_SW, DIR_S, DIR_SE} {
+		switch getByte(c + v) {
+		case '.':
+			sOpen++
+		case '|':
+			sTree++
+		case '#':
+			sLmbr++
+		}
+	}
+	return sOpen, sTree, sLmbr
+}
+
+func printScan() {
+	for i := 0; i < len(scan)/width; i++ {
+		fmt.Println(string(scan[i*width : (i+1)*width]))
+	}
+}
+
+// getByte pulls a byte from the given position in the scan
+func getByte(pos complex64) byte {
+	//idx := int(real(pos)) + int(imag(pos))*width
+	if int(real(pos)) < 0 || int(imag(pos)) < 0 || int(real(pos)) >= width || int(imag(pos)) >= height {
+		return 0
+	}
+	return scan[int(real(pos))+int(imag(pos))*width]
+}
+
+func getPosComplex(x, y int) complex64 {
+	return complex(float32(x), float32(y))
+}
+
+func getPosFromInt(i int) complex64 {
+	return complex(float32(i%width), float32(i/width))
+}
+
+func getIdxFromPos(pos complex64) int {
+	return int(real(pos)) + int(imag(pos))*width
+}
+
+func getCoordString(p complex64) string {
+	return fmt.Sprintf("(%d,%d [%d])", int(real(p)), int(imag(p)), getIdxFromPos(p))
+}
+
+func stdinToByteSlice() {
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		s := scanner.Bytes()
+		if width == 0 {
+			width = len(s)
+		}
+		scan = append(scan, s...)
+		height++
+	}
+}