62 lines
1.4 KiB
Go
62 lines
1.4 KiB
Go
package collatz
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import (
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"collatz/parsing"
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"fmt"
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"math/big"
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)
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type Calculator struct {
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parser parsing.Parser
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three *big.Int
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two *big.Int
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one *big.Int
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sequence Sequence
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}
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type Sequence struct {
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Iterations int
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Sequence []*big.Int
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}
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func NewCalculator(parser parsing.Parser) *Calculator {
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r := &Calculator{
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parser: parser,
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three: big.NewInt(3),
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two: big.NewInt(2),
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one: big.NewInt(1),
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}
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return r
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}
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func (calc *Calculator) CalculateCollatz() (Sequence, error) {
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number, err := calc.parser.Parse()
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if err != nil {
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return Sequence{}, fmt.Errorf("couldn't parse input: %w", err)
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}
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calc.sequence = Sequence{Iterations: 0}
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calc.sequence.Sequence = append(calc.sequence.Sequence, new(big.Int).Set(number))
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err = calc.calculateNextCollatzNumber(*number)
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if err != nil {
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return Sequence{}, err
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}
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return calc.sequence, nil
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}
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func (calc *Calculator) calculateNextCollatzNumber(in big.Int) error {
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if in.Cmp(calc.one) < 0 {
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return fmt.Errorf("must be greater than 0")
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}
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if in.Cmp(calc.one) == 0 {
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return nil
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}
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var newNumber *big.Int
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if new(big.Int).And(&in, calc.one).Cmp(calc.one) == 0 {
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newNumber = new(big.Int).Add(new(big.Int).Mul(&in, calc.three), calc.one)
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} else {
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newNumber = new(big.Int).Div(&in, calc.two)
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}
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calc.sequence.Iterations++
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calc.sequence.Sequence = append(calc.sequence.Sequence, newNumber)
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return calc.calculateNextCollatzNumber(*newNumber)
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}
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