本系列整理了10个工作量和难度适中的Golang小项目，适合已经掌握Go语法的工程师进一步熟练语法和常用库的用法。
问题描述：
有一组非负整数，实现一个位向量类型，能在O(1)时间内完成插入、删除和查找等操作。
要点：
实现Has(uint)、Add(uint)、Remove(uint)、Clear()、Copy()、String()、AddAll(…uint)、UnionWith()、IntersectWith()、DifferenceWith()、SymmetricDifference()方法。
拓展：
使用uint存储而不是uint32或uint64这样限定字长的类型。
代码实现：
import (
"bytes"
"fmt"
)
func (s *IntSet)countBit(n uint)int{
count := 0
for n != 0{
n = n & ( n - 1 )
count += 1
}
return count
}
func (s *IntSet)calWordBit(x int)(word int, bit uint) {
word, bit = x / wordSize, uint(x%wordSize)
return
}
const wordSize = 32 << (^uint(0) >> 63)
// An IntSet is a set of small non-negative integers.
// Its zero value represents the empty set.
type IntSet struct {
words []uint
}
// Has reports whether the set contains the non-negative value x.
func (s *IntSet) Has(x int) bool {
word, bit := s.calWordBit(x)
return word < len(s.words) && s.words[word]&(1< } // Add adds the non-negative value x to the set. func (s *IntSet) Add(x int) { word, bit := s.calWordBit(x) for word >= len(s.words) { s.words = append(s.words, 0) } s.words[word] |= 1 << bit } func (s *IntSet) AddAll(nums ...int) { for _, n := range nums { s.Add(n) } } // 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) } } } // Set s to the intersection of s and t. func (s *IntSet) IntersectWith(t *IntSet) { for i, tword := range t.words { if i < len(s.words) { s.words[i] &= tword } else { s.words = append(s.words, tword) } } } // Set s to the difference of s and t. func (s *IntSet) DifferenceWith(t *IntSet) { for i, tword := range t.words { if i < len(s.words) { s.words[i] &^= tword } else { s.words = append(s.words, tword) } } } // Set s to the symmetric difference of s and t. func (s *IntSet) SymmetricDifference(t *IntSet) { for i, tword := range t.words { if i < len(s.words) { s.words[i] ^= tword } else { s.words = append(s.words, tword) } } } // return the number of elements func (s *IntSet) Len() int { count := 0 for _, word := range s.words { count += s.countBit(word) } return count } // remove x from the set func (s *IntSet) Remove(x int) { word, bit := s.calWordBit(x) s.words[word] &^= 1 << bit } // remove all elements from the set func (s *IntSet) Clear() { for i := range s.words { s.words[i] = 0 } } // return a copy of the set func (s *IntSet) Copy() *IntSet { new := &IntSet{} new.words = make([]uint, len(s.words)) copy(new.words, s.words) return new } // 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 < wordSize; j++ { if word&(1< if buf.Len() > len("{") { buf.WriteByte(' ') } fmt.Fprintf(&buf, "%d", wordSize*i+j) } } } buf.WriteByte('}') return buf.String() } // Return set elements. func (s *IntSet) Elems() []int { e := make([]int, 0) for i, word := range s.words { for j := 0; j < wordSize; j++ { if word&(1< e = append(e, i*wordSize+j) } } } return e }