add: string quiz + execises

19-strings-runes-bytes/questions/README.md

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+# Strings, Runes and Bytes Quiz
+
+## Which byte slice below equals to the "keeper" string?
+```go
+// Here are the corresponding code points for the runes of "keeper":
+// k => 107
+// e => 101
+// p => 112
+// r => 114
+```
+1. []byte{107, 101, 101, 112, 101, 114} *CORRECT*
+2. []byte{112, 101, 101, 112, 114, 101}
+3. []byte{114, 101, 112, 101, 101, 112}
+4. []byte{112, 101, 101, 114, 107, 101}
+
+
+## What does this code print?
+```go
+// Code points:
+// g => 103
+// o => 111
+fmt.Println(string(103), string(111))
+```
+1. 103 111
+2. g o *CORRECT*
+3. n o
+4. "103 111"
+
+
+## What does this code print?
+```go
+const word = "gökyüzü"
+bword := []byte(word)
+
+// ö => 2 bytes
+// ü => 2 bytes
+fmt.Println(utf8.RuneCount(bword), len(word), len(string(word[1])))
+```
+1. 7 10 2 *CORRECT*
+2. 10 7 1
+3. 10 7 2
+4. 7 7 1
+
+
+## Which one below is true?
+1. for range loops over the bytes of a string
+2. for range loops over the runes of a string *CORRECT*
+
+
+## For a utf-8 encoded string value, which one below is true?
+1. runes always start and end in the same indexes
+2. runes may start and end in different indexes *CORRECT*
+3. bytes may start and end in different indexes
+
+
+
+## Why can't you change the bytes of a string value?
+1. Strings values are immutable byte slices
+2. Strings are used a lot so they are being shared behind the scenes
+3. All of above *CORRECT*