51 lines
1.4 KiB
Kotlin
51 lines
1.4 KiB
Kotlin
/**
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* File: fractional_knapsack.kt
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* Created Time: 2024-01-25
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* Author: curtishd (1023632660@qq.com)
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*/
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package chapter_greedy
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/* Item */
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class Item(
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val w: Int, // Item
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val v: Int // Item value
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)
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/* Fractional knapsack: Greedy */
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fun fractionalKnapsack(wgt: IntArray, _val: IntArray, c: Int): Double {
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// Create an item list, containing two properties: weight, value
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var cap = c
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val items = arrayOfNulls<Item>(wgt.size)
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for (i in wgt.indices) {
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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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items.sortBy { item: Item? -> -(item!!.v.toDouble() / item.w) }
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// Loop for greedy selection
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var res = 0.0
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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 += 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 += item.v.toDouble() / item.w * 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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/* Driver Code */
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fun main() {
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val wgt = intArrayOf(10, 20, 30, 40, 50)
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val _val = intArrayOf(50, 120, 150, 210, 240)
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val cap = 50
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// Greedy algorithm
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val res = fractionalKnapsack(wgt, _val, cap)
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println("Maximum value of items without exceeding bag capacity = $res")
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} |