add: array led clock exercises

15-arrays-project-clock/exercises/04-ticker/main.go

@@ -0,0 +1,113 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Ticker: Slide the Clock
+//
+//  Your goal is slide the placeholders every second.
+//  Please run the solution to see it in action.
+//
+//
+//  THIS IS A HARD EXERCISE:
+//  + It will take you days but it will worth it.
+//  + For experienced developers, this can take an hour or so.
+//
+//
+//  1. You need to determine the starting and the ending digits to create
+//     the sliding effect.
+//
+//
+//  2. Each second, start from the next placeholder, skip the previous one.
+//     This means: Only draw the next placeholders.
+//
+//     Like this:
+//
+//     12:40:31
+//     2:40:31
+//     40:31
+//     0:31
+//     :31
+//     31
+//     1
+//
+//
+//  3. After the last placeholder is displayed, fill the lines for the missing
+//     placeholders, and then start from the first placeholder. Draw it to the
+//     right part of the screen.
+//
+//     Like this:
+//
+//     12:40:31
+//     2:40:31
+//     40:31
+//     0:31
+//     :31
+//     31
+//     1
+//            1
+//           31
+//          :31
+//         0:31
+//        40:31
+//       :40:31
+//      2:40:31
+//     12:40:31
+//
+//     As you can see, you need to draw the clock from the right part of the
+//     screen, beginning from the first placeholder.
+//
+//
+// HINTS
+//   + You would need to clear the screen inside the loop instead of once.
+//     Otherwise the previous placeholders will be left on the screen.
+//
+//
+// EXPECTED OUTPUT
+//   Please run the solution to see it in action. Do not look at the source-code
+//   though.
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	screen.Clear()
+
+	for {
+		screen.MoveTopLeft()
+
+		now := time.Now()
+		hour, min, sec := now.Hour(), now.Minute(), now.Second()
+
+		clock := [...]placeholder{
+			digits[hour/10], digits[hour%10],
+			colon,
+			digits[min/10], digits[min%10],
+			colon,
+			digits[sec/10], digits[sec%10],
+		}
+
+		for line := range clock[0] {
+			for index, digit := range clock {
+				next := clock[index][line]
+				if digit == colon && sec%2 == 0 {
+					next = "   "
+				}
+				fmt.Print(next, "  ")
+			}
+			fmt.Println()
+		}
+
+		time.Sleep(time.Second)
+	}
+}