Day 8 solution

eight/display.go

@@ -0,0 +1,195 @@
+package eight
+
+import (
+	"bufio"
+	"os"
+	"sort"
+	"strings"
+)
+
+const (
+	one   = 2
+	four  = 4
+	seven = 3
+	eight = 7
+)
+
+type output struct {
+	signals []string
+	outputs []string
+}
+
+type display struct {
+	outputs []output
+}
+
+func (d *display) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		o := output{}
+
+		insOuts := strings.Split(scanner.Text(), " | ")
+
+		o.signals = strings.Split(insOuts[0], " ")
+		o.outputs = strings.Split(insOuts[1], " ")
+
+		d.outputs = append(d.outputs, o)
+	}
+	return nil
+}
+
+func (d *display) uniqueOuputs() int {
+	count := 0
+	for _, o := range d.outputs {
+		for _, s := range o.outputs {
+			switch len(s) {
+			case one, four, seven, eight:
+				count++
+			}
+		}
+	}
+
+	return count
+}
+
+func (o *output) decode() (value int) {
+	decoded := make(map[string]int, 10)
+	twoThreeFive := []string{}
+	zeroSixNine := []string{}
+
+	sortedSignals := []string{}
+	for _, s := range o.signals {
+		segments := sort.StringSlice(strings.Split(s, ""))
+		sort.Sort(segments)
+		sortedSignals = append(sortedSignals, strings.Join(segments, ""))
+	}
+
+	// Find known digits
+	for _, s := range sortedSignals {
+		switch len(s) {
+		case one:
+			decoded[s] = 1
+		case four:
+			decoded[s] = 4
+		case seven:
+			decoded[s] = 7
+		case eight:
+			decoded[s] = 8
+		case 5:
+			twoThreeFive = append(twoThreeFive, s)
+		case 6:
+			zeroSixNine = append(zeroSixNine, s)
+		}
+	}
+
+	// Decode twoThreeFive
+	twoFive := []string{}
+	// Find 3 string
+	for s, v := range decoded {
+		if v == 1 {
+			for _, v := range twoThreeFive {
+				sharedSegments := 0
+				for _, segment := range s {
+					if strings.Contains(v, string(segment)) {
+						sharedSegments++
+					}
+				}
+				if sharedSegments == 2 {
+					decoded[v] = 3
+				} else {
+					twoFive = append(twoFive, v)
+				}
+			}
+		}
+	}
+	// Find 5 and 2 string
+	for s, v := range decoded {
+		if v == 4 {
+			for _, v := range twoFive {
+				sharedSegments := 0
+				for _, segment := range s {
+					if strings.Contains(v, string(segment)) {
+						sharedSegments++
+					}
+				}
+				if sharedSegments == 3 {
+					decoded[v] = 5
+				} else {
+					decoded[v] = 2
+				}
+			}
+		}
+	}
+
+	// Decode zeroSixNine
+	// Find 0 string
+	sixNine := []string{}
+	for s, v := range decoded {
+		if v == 5 {
+			for _, v := range zeroSixNine {
+				sharedSegments := 0
+				for _, segment := range s {
+					if strings.Contains(v, string(segment)) {
+						sharedSegments++
+					}
+				}
+				if sharedSegments != 5 {
+					decoded[v] = 0
+				} else {
+					sixNine = append(sixNine, v)
+				}
+			}
+		}
+	}
+
+	// Find the 9 and 6 strings
+	for s, v := range decoded {
+		if v == 1 {
+			for _, v := range sixNine {
+				sharedSegments := 0
+				for _, segment := range s {
+					if strings.Contains(v, string(segment)) {
+						sharedSegments++
+					}
+				}
+				if sharedSegments == 2 {
+					decoded[v] = 9
+				} else {
+					decoded[v] = 6
+				}
+			}
+		}
+	}
+
+	for i, signal := range o.outputs {
+		scale := 1
+		switch i {
+		case 0:
+			scale = 1000
+		case 1:
+			scale = 100
+		case 2:
+			scale = 10
+		}
+
+		segments := sort.StringSlice(strings.Split(signal, ""))
+		sort.Sort(segments)
+		sortedSignal := strings.Join(segments, "")
+
+		value += scale * decoded[sortedSignal]
+	}
+
+	return value
+}
+
+func (d *display) outputSum() (sum int) {
+	for _, o := range d.outputs {
+		sum += o.decode()
+	}
+	return sum
+}