106 lines
2.6 KiB
Go
106 lines
2.6 KiB
Go
/*
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Copyright © 2025 filifa
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package cmd
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import (
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"errors"
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"fmt"
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"log"
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"math/big"
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"github.com/spf13/cobra"
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)
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func computeSqrtRepetend(x *big.Int) ([]*big.Int, error) {
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m := big.NewInt(0)
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d := big.NewInt(1)
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a0 := new(big.Int).Sqrt(x)
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s := new(big.Int).Exp(a0, big.NewInt(2), nil)
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if x.Cmp(s) == 0 {
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return nil, errors.New("input is a perfect square")
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}
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repetend := make([]*big.Int, 0)
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a := new(big.Int).Set(a0)
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twoa0 := new(big.Int).Mul(big.NewInt(2), a0)
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for a.Cmp(twoa0) != 0 {
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// m = d * a - m
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tmp := new(big.Int)
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m.Sub(tmp.Mul(d, a), m)
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// d = (x - m^2) // d
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tmp.Exp(m, big.NewInt(2), nil)
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d.Div(tmp.Sub(x, tmp), d)
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// a = (a0 + m) // d
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a.Div(tmp.Add(a0, m), d)
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repetend = append(repetend, new(big.Int).Set(a))
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}
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return repetend, nil
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}
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func sqrtRepetend(cmd *cobra.Command, args []string) {
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x := new(big.Int)
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for _, s := range args {
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_, ok := x.SetString(s, 10)
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if !ok {
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log.Print("invalid input " + s)
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continue
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}
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repetend, err := computeSqrtRepetend(x)
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if err != nil {
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log.Print(s + " is a perfect square")
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continue
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}
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fmt.Print(repetend[0])
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for _, r := range repetend[1:] {
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fmt.Printf(" %s", r)
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}
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fmt.Println()
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}
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}
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// sqrtRepetendCmd represents the sqrtRepetend command
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var sqrtRepetendCmd = &cobra.Command{
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Use: "sqrt-repetend N [N ...]",
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Short: "Compute the repetend of the square root of the input",
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Long: `Compute the repetend of the square root of the input.`,
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Args: cobra.MinimumNArgs(1),
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Run: sqrtRepetend,
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}
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func init() {
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rootCmd.AddCommand(sqrtRepetendCmd)
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// Here you will define your flags and configuration settings.
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// Cobra supports Persistent Flags which will work for this command
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// and all subcommands, e.g.:
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// sqrtRepetendCmd.PersistentFlags().String("foo", "", "A help for foo")
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// Cobra supports local flags which will only run when this command
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// is called directly, e.g.:
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// sqrtRepetendCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
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}
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