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107 lines
2.6 KiB
107 lines
2.6 KiB
package main
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import (
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"math/rand"
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"sort"
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)
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// combinations takes input in the form of a map of item lists, and returns a
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// list of all combinations of each item for each key. E.g.:
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//
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// {"foo": [1, 2, 3], "bar": [4, 5, 6]}
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//
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// Will return the following maps:
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//
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// {"foo": 1, "bar": 4}
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// {"foo": 1, "bar": 5}
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// {"foo": 1, "bar": 6}
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// {"foo": 2, "bar": 4}
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// {"foo": 2, "bar": 5}
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// {"foo": 2, "bar": 6}
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// {"foo": 3, "bar": 4}
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// {"foo": 3, "bar": 5}
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// {"foo": 3, "bar": 6}
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func combinations(items map[string][]interface{}) []map[string]interface{} {
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keys := []string{}
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for key := range items {
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keys = append(keys, key)
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}
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sort.Strings(keys)
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return combiner(map[string]interface{}{}, keys, items)
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}
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// combiner is a utility function for combinations.
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func combiner(head map[string]interface{}, pending []string, items map[string][]interface{}) []map[string]interface{} {
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if len(pending) == 0 {
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return []map[string]interface{}{head}
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}
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key, pending := pending[0], pending[1:]
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result := []map[string]interface{}{}
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for _, value := range items[key] {
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path := map[string]interface{}{}
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for k, v := range head {
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path[k] = v
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}
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path[key] = value
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result = append(result, combiner(path, pending, items)...)
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}
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return result
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}
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// uniformChoice chooses a single random item from the argument list, uniformly weighted.
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type uniformChoice []interface{}
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func (uc uniformChoice) Choose(r *rand.Rand) interface{} {
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return uc[r.Intn(len(uc))]
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}
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// weightedChoice chooses a single random key from a map of keys and weights.
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type weightedChoice map[interface{}]uint
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func (wc weightedChoice) Choose(r *rand.Rand) interface{} {
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total := 0
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choices := make([]interface{}, 0, len(wc))
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for choice, weight := range wc {
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total += int(weight)
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choices = append(choices, choice)
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}
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rem := r.Intn(total)
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for _, choice := range choices {
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rem -= int(wc[choice])
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if rem <= 0 {
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return choice
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}
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}
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return nil
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}
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// probSetChoice picks a set of strings based on each string's probability (0-1).
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type probSetChoice map[string]float64
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func (pc probSetChoice) Choose(r *rand.Rand) []string {
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choices := []string{}
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for item, prob := range pc {
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if r.Float64() <= prob {
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choices = append(choices, item)
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}
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}
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return choices
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}
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// uniformSetChoice picks a set of strings with uniform probability, picking at least one.
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type uniformSetChoice []string
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func (usc uniformSetChoice) Choose(r *rand.Rand) []string {
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choices := []string{}
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indexes := r.Perm(len(usc))
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if len(indexes) > 1 {
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indexes = indexes[:1+r.Intn(len(indexes)-1)]
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}
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for _, i := range indexes {
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choices = append(choices, usc[i])
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}
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return choices
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}
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