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package iter
import "math/rand"
type seq struct {
i []int
}
// Creates sequence of values from [0, n)
func newSeq(n int) seq {
return seq{make([]int, n, n)}
}
func (me seq) Index(i int) (ret int) {
ret = me.i[i]
if ret == 0 {
ret = i
}
return
}
func (me seq) Len() int {
return len(me.i)
}
// Remove the nth value from the sequence.
func (me *seq) DeleteIndex(index int) {
me.i[index] = me.Index(me.Len() - 1)
me.i = me.i[:me.Len()-1]
}
func ForPerm(n int, callback func(i int) (more bool)) bool {
s := newSeq(n)
for s.Len() > 0 {
r := rand.Intn(s.Len())
if !callback(s.Index(r)) {
return false
}
s.DeleteIndex(r)
}
return true
}
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