add: new exercises to bouncing ball

18-project-bouncing-ball/exercises/05-no-slice/main.go

@@ -0,0 +1,110 @@
+// 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/
+//
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+	"github.com/mattn/go-runewidth"
+)
+
+// ---------------------------------------------------------
+// EXERCISE: No Slice
+//
+//   Can you modify the program so that it doesn't use a
+//   slice for the board. You can use a slice for the buffer
+//   though.
+//
+//   In this exercise, you'll understand that you don't
+//   have to use slices in any problem you encounter with.
+//
+//   See what it feels like not using a slice for this
+//   solution.
+//
+//   Think about why you have to use a slice for the buffer?
+//
+//   Can there be any other solution?
+//
+// ---------------------------------------------------------
+
+func main() {
+	const (
+		cellEmpty = ' '
+		cellBall  = '⚾'
+
+		maxFrames = 1200
+		speed     = time.Second / 20
+
+		ivx, ivy = 1, 1 // initial velocities
+	)
+
+	var (
+		px, py   int        // ball position
+		ppx, ppy int        // previous ball position
+		vx, vy   = ivx, ivy // velocities
+
+		cell rune // current cell (for caching)
+	)
+
+	width, height := screen.Size()
+	width /= runewidth.RuneWidth(cellBall)
+	height-- // there is a 1 pixel border in my terminal
+
+	// REMOVE THIS: create a single-dimensional board
+	board := make([]bool, width*height)
+
+	// create a drawing buffer
+	// *2 for extra spaces
+	// +1 for newlines
+	buf := make([]rune, 0, (width*2+1)*height)
+
+	screen.Clear()
+
+	for i := 0; i < maxFrames; i++ {
+		// calculate the next ball position
+		px += vx
+		py += vy
+
+		// when the ball hits a border reverse its direction
+		if px <= 0 || px >= width-ivx {
+			vx *= -1
+		}
+		if py <= 0 || py >= height-ivy {
+			vy *= -1
+		}
+
+		// remove the previous ball and put the new ball
+		pos := py*width + px
+		ppos := ppy*width + ppx
+		ppx, ppy = px, py
+
+		board[pos], board[ppos] = true, false
+
+		buf = buf[:0]
+
+		for y := 0; y < height; y++ {
+			for x := 0; x < width; x++ {
+				cell = cellEmpty
+
+				if board[y*width+x] {
+					cell = cellBall
+				}
+
+				buf = append(buf, cell, ' ')
+			}
+			buf = append(buf, '\n')
+		}
+
+		screen.MoveTopLeft()
+		fmt.Print(string(buf))
+
+		time.Sleep(speed)
+	}
+}

18-project-bouncing-ball/exercises/05-no-slice/solution/main.go

@@ -0,0 +1,81 @@
+// 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/
+//
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+	"github.com/mattn/go-runewidth"
+)
+
+func main() {
+	const (
+		cellEmpty = ' '
+		cellBall  = '⚾'
+
+		maxFrames = 1200
+		speed     = time.Second / 20
+
+		// initial velocities
+		ivx, ivy = 1, 1
+	)
+
+	var (
+		px, py int        // ball position
+		vx, vy = ivx, ivy // velocities
+
+		cell rune // current cell (for caching)
+	)
+
+	width, height := screen.Size()
+	width /= runewidth.RuneWidth(cellBall)
+	height-- // there is a 1 pixel border in my terminal
+
+	// create a drawing buffer
+	// *2 for extra spaces
+	// +1 for newlines
+	buf := make([]rune, 0, (width*2+1)*height)
+
+	screen.Clear()
+
+	for i := 0; i < maxFrames; i++ {
+		// calculate the next ball position
+		px += vx
+		py += vy
+
+		// when the ball hits a border reverse its direction
+		if px <= 0 || px >= width-1 {
+			vx *= -1
+		}
+		if py <= 0 || py >= height-1 {
+			vy *= -1
+		}
+
+		buf = buf[:0]
+
+		for y := 0; y < height; y++ {
+			for x := 0; x < width; x++ {
+				cell = cellEmpty
+
+				if px == x && py == y {
+					cell = cellBall
+				}
+
+				buf = append(buf, cell, ' ')
+			}
+			buf = append(buf, '\n')
+		}
+
+		screen.MoveTopLeft()
+		fmt.Print(string(buf))
+
+		time.Sleep(speed)
+	}
+}

18-project-bouncing-ball/exercises/README.md

@@ -1,13 +1,22 @@
-# Exercises
+# Bouncing Ball Exercises
 
-1. **[Adjust the width and height automatically](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/01-width-and-height)**
+1. **[Find the Bug](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/01-find-the-bug)**
+
+    There is a bug in the bouncing ball code. Test yourself that you really understand how the backing arrays work.
+
+
+2. **[Adjust the width and height automatically](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/02-width-and-height)**
 
     In this exercise, your goal is getting the width and height of the terminal screen from your operating system (instead of setting the width and height manually).
 
-2. **[Previous positions](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/02-previous-positions)**
+3. **[Previous positions](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/03-previous-positions)**
 
     Let's optimize the program once more. This time you're going to optimize the clearing off the previous positions.
 
-3. **[Use a single dimensional slice](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/03-single-dimensional)**
+4. **[Use a single dimensional slice](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/04-single-dimensional)**
 
-    For the board slice, instead of using a multi-dimensional slice, let's use a single-dimensional slice. In this exercise, you'll understand and deeply internalize why I've used a multi-dimensional board slice.
+    For the board slice, instead of using a multi-dimensional slice, let's use a single-dimensional slice. In this exercise, you'll understand and deeply internalize why I've used a multi-dimensional board slice.
+
+5. **[Don't use a slice for the board](https://github.com/inancgumus/learngo/tree/master/18-project-bouncing-ball/exercises/05-no-slice)**
+
+    Expand your horizon: Don't use a slice for the board. You only need a slice for the buffer, only that.