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60 lines
1.5 KiB
60 lines
1.5 KiB
/*
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* File: coin_change_greedy.rs
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* Created Time: 2023-07-22
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* Author: night-cruise (2586447362@qq.com)
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*/
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/* 物品 */
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struct Item {
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w: i32, // 物品重量
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v: i32, // 物品價值
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}
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impl Item {
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fn new(w: i32, v: i32) -> Self {
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Self { w, v }
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}
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}
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/* 分數背包：貪婪 */
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fn fractional_knapsack(wgt: &[i32], val: &[i32], mut cap: i32) -> f64 {
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// 建立物品串列，包含兩個屬性：重量、價值
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let mut items = wgt
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.iter()
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.zip(val.iter())
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.map(|(&w, &v)| Item::new(w, v))
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.collect::<Vec<Item>>();
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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_by(|a, b| {
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(b.v as f64 / b.w as f64)
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.partial_cmp(&(a.v as f64 / a.w as f64))
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.unwrap()
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});
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// 迴圈貪婪選擇
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let mut res = 0.0;
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for item in &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 as f64;
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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 as f64 / item.w as f64 * cap as f64;
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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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res
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}
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/* Driver Code */
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fn main() {
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let wgt = [10, 20, 30, 40, 50];
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let val = [50, 120, 150, 210, 240];
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let cap = 50;
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// 貪婪演算法
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let res = fractional_knapsack(&wgt, &val, cap);
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println!("不超過背包容量的最大物品價值為 {}", res);
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}
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