Golang 实现Bit数组

**

《The Go Programming Language》 笔记

**

import (
    "bytes"
    "fmt"
)

const target int = 32 << (^uint(0) >> 63) //判断当前系统是32位还是64位

type IntSet struct {
    words []uint
}

func (s *IntSet) Has(x int) bool {
    word, bit := x/target, uint(x%target)
    return word < len(s.words) && s.words[word]&(1<0
}

func (s *IntSet) Add(numbers ...int) {
    for _, numebr := range numbers {
        x := numebr
        word, bit := x/target, uint(x%target)
        for word >= len(s.words) {
            s.words = append(s.words, 0)
        }
        s.words[word] |= 1 << bit
    }
}

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<0 {
                if buf.Len() > len("{") {
                    buf.WriteByte(' ')
                }
                fmt.Fprintf(&buf, "%d", 64*i+j)
            }
        }
    }
    buf.WriteByte('}')
    return buf.String()
}

//并集，合并s,t
func UnionWith(s, t *IntSet) *IntSet {
    uw := &IntSet{}
    slen, tlen := len(s.words), len(t.words)
    minlen := slen
    if minlen > tlen {
        minlen = tlen
    }
    for i := 0; i < minlen; i++ {
        uw.words = append(uw.words, s.words[i]|t.words[i])
    }
    if minlen == tlen {
        union(uw, s, minlen, slen)
    } else {
        union(uw, t, minlen, tlen)
    }
    return uw
}

//交集,元素在s,t中均出现
func InersectWith(s, t *IntSet) *IntSet {
    iw := &IntSet{}
    slen, tlen := len(s.words), len(t.words)
    minlen := slen
    if minlen > tlen {
        minlen = tlen
    }
    for i := 0; i < minlen; i++ {
        iw.words = append(iw.words, s.words[i]&t.words[i])
    }
    if minlen == tlen { //s元素更多, 多余的元素全部置为0
        for minlen < slen {
            iw.words = append(iw.words, s.words[minlen]&0)
            minlen++
        }
    }
    return iw
}

//差集，元素出现在s，未出现在t
func DifferenceWith(s, t *IntSet) *IntSet {
    dw := &IntSet{}
    slen, tlen := len(s.words), len(t.words)
    minlen := slen
    if minlen > tlen {
        minlen = tlen
    }
    for i := 0; i < minlen; i++ {
        mask := s.words[i] & t.words[i]
        dw.words = append(dw.words, s.words[i]^mask)
    }
    if minlen == tlen && minlen < slen {
        union(dw, s, minlen, slen)
    }
    return dw
}

//并差集，元素出现在s但未出现在t，或者元素出现在t但未出现在s
func SymmetricDifference(s, t *IntSet) *IntSet {
    sd := &IntSet{}
    slen, tlen := len(s.words), len(t.words)
    minlen := slen
    if minlen > tlen {
        minlen = tlen
    }
    for i := 0; i < minlen; i++ {
        sd.words = append(sd.words, s.words[i]^t.words[i])
    }
    if minlen == tlen {
        union(sd, s, minlen, slen)
    } else {
        union(sd, t, minlen, tlen)
    }
    return sd
}

//从tmplen开始，将is中的元素复制到res
func union(res, is *IntSet, tmplen, xlen int) {
    for tmplen < xlen {
        res.words = append(res.words, is.words[tmplen])
        tmplen++
    }
}

func main() {
    var x, y IntSet
    x.Add(0)
    x.Add(1, 3, 5, 7)
    x.Add(9)
    x.Add(63)
    x.Add(100)
    fmt.Println("x : ", x.String())

    y.Add(9)
    y.Add(42)
    y.Add(7)
    y.Add(5)
    fmt.Println("y : ", y.String())

    result1 := UnionWith(&x, &y)
    fmt.Println("x UnionWith y : ", result1.String())
    result2 := InersectWith(&x, &y)
    fmt.Println("x InersectWith y : ", result2.String())
    result3 := DifferenceWith(&x, &y)
    fmt.Println("x DifferenceWith y : ", result3.String())
    result4 := SymmetricDifference(&x, &y)
    fmt.Println("x SymmetricDifference y : ", result4.String())

}