add: new exercises to bouncing ball

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)
+	}
+}