ch6: fix code format

ch6/ch6-05.md

@@ -4,38 +4,38 @@ Go語言里的集合一般會用map[T]bool這種形式來表示，T代表元素
 
 一個bit數組通常會用一個無符號數或者稱之爲“字”的slice或者來表示，每一個元素的每一位都表示集合里的一個值。當集合的第i位被設置時，我們才説這個集合包含元素i。下面的這個程序展示了一個簡單的bit數組類型，併且實現了三個函數來對這個bit數組來進行操作：
 
+<u><i>gopl.io/ch6/intset</i></u>
 ```go
-gopl.io/ch6/intset
 // An IntSet is a set of small non-negative integers.
 // Its zero value represents the empty set.
 type IntSet struct {
-    words []uint64
+	words []uint64
 }
 
 // Has reports whether the set contains the non-negative value x.
 func (s *IntSet) Has(x int) bool {
-    word, bit := x/64, uint(x%64)
-    return word < len(s.words) && s.words[word]&(1<<bit) != 0
+	word, bit := x/64, uint(x%64)
+	return word < len(s.words) && s.words[word]&(1<<bit) != 0
 }
 
 // Add adds the non-negative value x to the set.
 func (s *IntSet) Add(x int) {
-    word, bit := x/64, uint(x%64)
-    for word >= len(s.words) {
-        s.words = append(s.words, 0)
-    }
-    s.words[word] |= 1 << bit
+	word, bit := x/64, uint(x%64)
+	for word >= len(s.words) {
+		s.words = append(s.words, 0)
+	}
+	s.words[word] |= 1 << bit
 }
 
 // UnionWith sets s to the union of s and t.
 func (s *IntSet) UnionWith(t *IntSet) {
-    for i, tword := range t.words {
-        if i < len(s.words) {
-            s.words[i] |= tword
-        } else {
-            s.words = append(s.words, tword)
-        }
-    }
+	for i, tword := range t.words {
+		if i < len(s.words) {
+			s.words[i] |= tword
+		} else {
+			s.words = append(s.words, tword)
+		}
+	}
 }
 
 ```
@@ -46,23 +46,23 @@ func (s *IntSet) UnionWith(t *IntSet) {
 ```go
 // String returns the set as a string of the form "{1 2 3}".
 func (s *IntSet) String() string {
-    var buf bytes.Buffer
-    buf.WriteByte('{')
-    for i, word := range s.words {
-        if word == 0 {
-            continue
-        }
-        for j := 0; j < 64; j++ {
-            if word&(1<<uint(j)) != 0 {
-                if buf.Len() > len("{") {
-                    buf.WriteByte('}')
-                }
-                fmt.Fprintf(&buf, "%d", 64*i+j)"}")}}
-            }
-        }
-    }
-    buf.WriteByte('}')
-    return buf.String()
+	var buf bytes.Buffer
+	buf.WriteByte('{')
+	for i, word := range s.words {
+		if word == 0 {
+			continue
+		}
+		for j := 0; j < 64; j++ {
+			if word&(1<<uint(j)) != 0 {
+				if buf.Len() > len("{") {
+					buf.WriteByte('}')
+				}
+				fmt.Fprintf(&buf, "%d", 64*i+j)"}")}}
+			}
+		}
+	}
+	buf.WriteByte('}')
+	return buf.String()
 }
 ```