51 lines
714 B
Go
51 lines
714 B
Go
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package main
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import (
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"cmp"
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"slices"
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)
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type Factor struct {
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factor int
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index int
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next int
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}
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func MakeFactor(factor int) Factor {
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return Factor{
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factor: factor,
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index: 0,
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next: factor,
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}
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}
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func (f *Factor) Update(ugly []int, last int) {
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if last != f.next {
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return
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}
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f.index++
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f.next = f.factor * ugly[f.index]
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}
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func nthUglyNumber(n int) int {
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ugly := make([]int, n)
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ugly[0] = 1
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factors := []Factor{
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MakeFactor(2), MakeFactor(3), MakeFactor(5),
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}
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for i := 1; i < n; i++ {
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ugly[i] = slices.MinFunc(factors, func(a, b Factor) int {
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return cmp.Compare(a.next, b.next)
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}).next
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for j, _ := range factors {
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factors[j].Update(ugly, ugly[i])
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}
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}
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return ugly[n-1]
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}
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