Data commit

Task/Reverse-a-string/Go/reverse-a-string.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+    "fmt"
+    "unicode"
+    "unicode/utf8"
+)
+
+// no encoding
+func reverseBytes(s string) string {
+    r := make([]byte, len(s))
+    for i := 0; i < len(s); i++ {
+        r[i] = s[len(s)-1-i]
+    }
+    return string(r)
+}
+
+// reverseCodePoints interprets its argument as UTF-8 and ignores bytes
+// that do not form valid UTF-8.  return value is UTF-8.
+func reverseCodePoints(s string) string {
+    r := make([]rune, len(s))
+    start := len(s)
+    for _, c := range s {
+        // quietly skip invalid UTF-8
+        if c != utf8.RuneError {
+            start--
+            r[start] = c
+        }
+    }
+    return string(r[start:])
+}
+
+// reversePreservingCombiningCharacters interprets its argument as UTF-8
+// and ignores bytes that do not form valid UTF-8.  return value is UTF-8.
+func reversePreservingCombiningCharacters(s string) string {
+    if s == "" {
+        return ""
+    }
+    p := []rune(s)
+    r := make([]rune, len(p))
+    start := len(r)
+    for i := 0; i < len(p); {
+        // quietly skip invalid UTF-8
+        if p[i] == utf8.RuneError {
+            i++
+            continue
+        }
+        j := i + 1
+        for j < len(p) && (unicode.Is(unicode.Mn, p[j]) ||
+            unicode.Is(unicode.Me, p[j]) || unicode.Is(unicode.Mc, p[j])) {
+            j++
+        }
+        for k := j - 1; k >= i; k-- {
+            start--
+            r[start] = p[k]
+        }
+        i = j
+    }
+    return (string(r[start:]))
+}
+
+func main() {
+    test("asdf")
+    test("as⃝df̅")
+}
+
+func test(s string) {
+    fmt.Println("\noriginal:      ", []byte(s), s)
+    r := reverseBytes(s)
+    fmt.Println("reversed bytes:", []byte(r), r)
+    fmt.Println("original code points:", []rune(s), s)
+    r = reverseCodePoints(s)
+    fmt.Println("reversed code points:", []rune(r), r)
+    r = reversePreservingCombiningCharacters(s)
+    fmt.Println("combining characters:", []rune(r), r)
+}