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* Modify method name to PascalCase(array and linked list) * Modify method name to PascalCase(backtracking) * Modify method name to PascalCase(computational complexity) * Modify method name to PascalCase(divide and conquer) * Modify method name to PascalCase(dynamic programming) * Modify method name to PascalCase(graph) * Modify method name to PascalCase(greedy) * Modify method name to PascalCase(hashing) * Modify method name to PascalCase(heap) * Modify method name to PascalCase(searching) * Modify method name to PascalCase(sorting) * Modify method name to PascalCase(stack and queue) * Modify method name to PascalCase(tree) * local check
57 lines
No EOL
1.7 KiB
C#
57 lines
No EOL
1.7 KiB
C#
/**
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* File: fractional_knapsack.cs
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* Created Time: 2023-07-21
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_greedy;
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/* 物品 */
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class Item {
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public int w; // 物品重量
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public int v; // 物品价值
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public Item(int w, int v) {
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this.w = w;
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this.v = v;
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}
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}
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public class fractional_knapsack {
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/* 分数背包:贪心 */
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public double FractionalKnapsack(int[] wgt, int[] val, int cap) {
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// 创建物品列表,包含两个属性:重量、价值
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Item[] items = new Item[wgt.Length];
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for (int i = 0; i < wgt.Length; i++) {
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items[i] = new Item(wgt[i], val[i]);
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}
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// 按照单位价值 item.v / item.w 从高到低进行排序
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Array.Sort(items, (x, y) => (y.v / y.w).CompareTo(x.v / x.w));
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// 循环贪心选择
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double res = 0;
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foreach (Item item in items) {
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if (item.w <= cap) {
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// 若剩余容量充足,则将当前物品整个装进背包
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res += item.v;
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cap -= item.w;
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} else {
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// 若剩余容量不足,则将当前物品的一部分装进背包
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res += (double)item.v / item.w * cap;
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// 已无剩余容量,因此跳出循环
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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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[Test]
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public void Test() {
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int[] wgt = { 10, 20, 30, 40, 50 };
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int[] val = { 50, 120, 150, 210, 240 };
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int cap = 50;
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// 贪心算法
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double res = FractionalKnapsack(wgt, val, cap);
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Console.WriteLine("不超过背包容量的最大物品价值为 " + res);
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}
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} |