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47 lines
1.3 KiB
47 lines
1.3 KiB
/**
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* File: fractional_knapsack.js
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* Created Time: 2023-09-02
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* Author: Justin (xiefahit@gmail.com)
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*/
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/* 物品 */
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class Item {
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constructor(w, v) {
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this.w = w; // 物品重量
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this.v = v; // 物品價值
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}
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}
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/* 分數背包：貪婪 */
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function fractionalKnapsack(wgt, val, cap) {
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// 建立物品串列，包含兩個屬性：重量、價值
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const items = wgt.map((w, i) => new Item(w, val[i]));
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// 按照單位價值 item.v / item.w 從高到低進行排序
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items.sort((a, b) => b.v / b.w - a.v / a.w);
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// 迴圈貪婪選擇
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let res = 0;
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for (const item of items) {
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if (item.w <= cap) {
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// 若剩餘容量充足，則將當前物品整個裝進背包
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res += item.v;
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cap -= item.w;
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} else {
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// 若剩餘容量不足，則將當前物品的一部分裝進背包
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res += (item.v / item.w) * cap;
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// 已無剩餘容量，因此跳出迴圈
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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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const wgt = [10, 20, 30, 40, 50];
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const val = [50, 120, 150, 210, 240];
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const cap = 50;
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const n = wgt.length;
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// 貪婪演算法
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const res = fractionalKnapsack(wgt, val, cap);
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console.log(`不超過背包容量的最大物品價值為 ${res}`);
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