add: loop for statement exercises

13-loops/exercises/07-multiplication-table-exercises/02-math-tables/solution/main.go

@@ -0,0 +1,85 @@
+// 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"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const (
+	validOps = "%*/+-"
+
+	usageMsg       = "Usage: [op=" + validOps + "] [size]"
+	sizeMissingMsg = "Size is missing"
+	invalidOpMsg   = `Invalid operator.
+Valid ops one of: ` + validOps
+
+	invalidOp = -1
+)
+
+func main() {
+	args := os.Args[1:]
+
+	switch l := len(args); {
+	case l == 1:
+		fmt.Println(sizeMissingMsg)
+		fallthrough
+	case l < 1:
+		fmt.Println(usageMsg)
+		return
+	}
+
+	op := args[0]
+	if strings.IndexAny(op, validOps) == invalidOp {
+		fmt.Println(invalidOpMsg)
+		return
+	}
+
+	size, err := strconv.Atoi(args[1])
+	if err != nil || size <= 0 {
+		fmt.Println("Wrong size")
+		return
+	}
+
+	fmt.Printf("%5s", op)
+	for i := 0; i <= size; i++ {
+		fmt.Printf("%5d", i)
+	}
+	fmt.Println()
+
+	for i := 0; i <= size; i++ {
+		fmt.Printf("%5d", i)
+
+		for j := 0; j <= size; j++ {
+			var res int
+
+			switch op {
+			case "*":
+				res = i * j
+			case "%":
+				if j != 0 {
+					res = i % j
+				}
+			case "/":
+				if j != 0 {
+					res = i / j
+				}
+			case "+":
+				res = i + j
+			case "-":
+				res = i - j
+			}
+
+			fmt.Printf("%5d", res)
+		}
+		fmt.Println()
+	}
+}