42 lines
1.1 KiB
Go
42 lines
1.1 KiB
Go
// File: fractional_knapsack.go
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// Created Time: 2023-07-23
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// Author: Reanon (793584285@qq.com)
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package chapter_greedy
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import "sort"
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/* Item */
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type Item struct {
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w int // Item weight
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v int // Item value
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}
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/* Fractional knapsack: Greedy */
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func fractionalKnapsack(wgt []int, val []int, cap int) float64 {
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// Create an item list, containing two properties: weight, value
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items := make([]Item, len(wgt))
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for i := 0; i < len(wgt); i++ {
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items[i] = Item{wgt[i], val[i]}
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}
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// Sort by unit value item.v / item.w from high to low
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sort.Slice(items, func(i, j int) bool {
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return float64(items[i].v)/float64(items[i].w) > float64(items[j].v)/float64(items[j].w)
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})
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// Loop for greedy selection
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res := 0.0
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for _, item := range items {
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if item.w <= cap {
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// If the remaining capacity is sufficient, put the entire item into the knapsack
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res += float64(item.v)
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cap -= item.w
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} else {
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// If the remaining capacity is insufficient, put part of the item into the knapsack
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res += float64(item.v) / float64(item.w) * float64(cap)
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// No remaining capacity left, thus break the loop
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break
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}
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}
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return res
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}
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