Merge pull request #508 from 01-edu/reachable_number

reachable_number subject

subjects/reachable_number.en.md

@@ -0,0 +1,42 @@
+## reachable_number
+
+### Instructions
+
+Let us define a function f(x) by the following: first we add 1 to x, and then while the last digit of the number equals 0, we shall be deleting 0. Let us call 'y' reachable if we can apply **f** to **x** (zero or more times), and get **y**. 102 is reachable from 10098: f(f(f(10098))) = f(f(10099)) = f(101) = f(102). Any number is reachable from itself. You are given a positive number **n**, count how many integers are reachable from **n**.
+
+### Expected function
+
+```go
+func Reachablenumber(n int) int {
+
+}
+```
+
+### Usage
+
+Here is a possible program to test your function :
+
+```go
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	fmt.Println(Reachablenumber(1))
+	fmt.Println(Reachablenumber(10))
+	fmt.Println(Reachablenumber(1001))
+}
+```
+
+And its output :
+
+```console
+student@ubuntu:~/[[ROOT]]/test$ go build
+student@ubuntu:~/[[ROOT]]/test$ ./test
+9
+19
+36
+student@ubuntu:~/[[ROOT]]/test$
+```