52 lines
1.2 KiB
Go
52 lines
1.2 KiB
Go
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package bitmap
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import "fmt"
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//位图
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type BitMap struct {
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bits []byte
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max int
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}
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//初始化一个BitMap
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//一个byte有8位,可代表8个数字,取余后加1为存放最大数所需的容量
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func NewBitMap(max int) *BitMap {
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bits := make([]byte, (max>>3)+1)
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return &BitMap{bits: bits, max: max}
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}
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//添加一个数字到位图
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//计算添加数字在数组中的索引index,一个索引可以存放8个数字
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//计算存放到索引下的第几个位置,一共0-7个位置
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//原索引下的内容与1左移到指定位置后做或运算
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func (b *BitMap) Add(num uint) {
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index := num >> 3
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pos := num & 0x07
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b.bits[index] |= 1 << pos
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}
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//判断一个数字是否在位图
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//找到数字所在的位置,然后做与运算
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func (b *BitMap) IsExist(num uint) bool {
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index := num >> 3
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pos := num & 0x07
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return b.bits[index]&(1<<pos) != 0
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}
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//删除一个数字在位图
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//找到数字所在的位置取反,然后与索引下的数字做与运算
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func (b *BitMap) Remove(num uint) {
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index := num >> 3
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pos := num & 0x07
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b.bits[index] = b.bits[index] & ^(1 << pos)
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}
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//位图的最大数字
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func (b *BitMap) Max() int {
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return b.max
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}
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func (b *BitMap) String() string {
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return fmt.Sprint(b.bits)
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}
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