58 lines
1.6 KiB
Swift
58 lines
1.6 KiB
Swift
/**
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* File: fractional_knapsack.swift
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* Created Time: 2023-09-03
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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/* Item */
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class Item {
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var w: Int // Item weight
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var v: Int // Item value
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init(w: Int, v: Int) {
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self.w = w
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self.v = v
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}
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}
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/* Fractional knapsack: Greedy */
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func fractionalKnapsack(wgt: [Int], val: [Int], cap: Int) -> Double {
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// Create an item list, containing two properties: weight, value
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var items = zip(wgt, val).map { Item(w: $0, v: $1) }
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// Sort by unit value item.v / item.w from high to low
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items.sort { -(Double($0.v) / Double($0.w)) < -(Double($1.v) / Double($1.w)) }
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// Loop for greedy selection
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var res = 0.0
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var cap = cap
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for item in 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 += Double(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 += Double(item.v) / Double(item.w) * Double(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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@main
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enum FractionalKnapsack {
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/* Driver Code */
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static func main() {
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// Item weight
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let wgt = [10, 20, 30, 40, 50]
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// Item value
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let val = [50, 120, 150, 210, 240]
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// Backpack capacity
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let cap = 50
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// Greedy algorithm
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let res = fractionalKnapsack(wgt: wgt, val: val, cap: cap)
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print("Maximum value of items within the backpack capacity = \(res)")
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}
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}
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