116 lines
2.7 KiB
Go
116 lines
2.7 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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"fmt"
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"math/big"
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"strconv"
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"github.com/spf13/cobra"
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)
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var partitionsN string
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var partitionsK string
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// given a slice where vals[i] = p_{k-1}(i) for a given k, nextPartition updates the slice so vals[i] = p_k(i) using the property that p_k(n) = p_k(n-k) + p_{k-1}(n)
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func nextPartition(k int, vals []*big.Int) {
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for i := 1; i < len(vals); i++ {
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if i-k >= 0 {
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vals[i].Add(vals[i], vals[i-k])
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}
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}
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}
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func p(n, k int) *big.Int {
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if n < 0 {
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return big.NewInt(0)
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}
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if k > n {
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k = n
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}
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vals := make([]*big.Int, n+1)
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for i := range vals {
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vals[i] = big.NewInt(0)
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}
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vals[0] = big.NewInt(1)
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for i := 1; i <= k; i++ {
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nextPartition(i, vals)
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}
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return vals[n]
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}
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func partitions(cmd *cobra.Command, args []string) {
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n, err := strconv.Atoi(partitionsN)
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if err != nil {
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cobra.CheckErr("invalid input " + partitionsN)
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}
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var k int
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if partitionsK == "" {
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k = n
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} else {
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var err error
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k, err = strconv.Atoi(partitionsK)
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if err != nil {
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cobra.CheckErr("invalid input " + partitionsK)
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}
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}
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if n < 0 {
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cobra.CheckErr("n must be nonnegative")
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}
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if k < 0 {
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cobra.CheckErr("k must be nonnegative")
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}
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z := p(n, k)
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fmt.Println(z)
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}
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// partitionsCmd represents the partitions command
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var partitionsCmd = &cobra.Command{
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Use: "partitions",
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Short: "Compute the number of partitions of an integer",
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Long: `Compute the number of partitions of an integer.`,
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Run: partitions,
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}
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func init() {
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rootCmd.AddCommand(partitionsCmd)
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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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// partitionsCmd.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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// partitionsCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
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partitionsCmd.Flags().StringVarP(&partitionsN, "number", "n", "", "number to compute partitions of")
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partitionsCmd.MarkFlagRequired("number")
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partitionsCmd.Flags().StringVarP(&partitionsK, "parts", "k", "", "maximum number of parts")
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}
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