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55 lines
1.6 KiB
55 lines
1.6 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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/* 零錢兌換：貪婪 */
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fn coin_change_greedy(coins: &[i32], mut amt: i32) -> i32 {
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// 假設 coins 串列有序
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let mut i = coins.len() - 1;
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let mut count = 0;
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// 迴圈進行貪婪選擇，直到無剩餘金額
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while amt > 0 {
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// 找到小於且最接近剩餘金額的硬幣
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while i > 0 && coins[i] > amt {
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i -= 1;
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}
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// 選擇 coins[i]
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amt -= coins[i];
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count += 1;
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}
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// 若未找到可行方案，則返回 -1
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if amt == 0 {
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count
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} else {
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-1
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}
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}
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/* Driver Code */
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fn main() {
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// 貪婪：能夠保證找到全域性最優解
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let coins = [1, 5, 10, 20, 50, 100];
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let amt = 186;
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let res = coin_change_greedy(&coins, amt);
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println!("\ncoins = {:?}, amt = {}", coins, amt);
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println!("湊到 {} 所需的最少硬幣數量為 {}", amt, res);
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// 貪婪：無法保證找到全域性最優解
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let coins = [1, 20, 50];
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let amt = 60;
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let res = coin_change_greedy(&coins, amt);
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println!("\ncoins = {:?}, amt = {}", coins, amt);
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println!("湊到 {} 所需的最少硬幣數量為 {}", amt, res);
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println!("實際上需要的最少數量為 3 ，即 20 + 20 + 20");
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// 貪婪：無法保證找到全域性最優解
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let coins = [1, 49, 50];
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let amt = 98;
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let res = coin_change_greedy(&coins, amt);
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println!("\ncoins = {:?}, amt = {}", coins, amt);
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println!("湊到 {} 所需的最少硬幣數量為 {}", amt, res);
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println!("實際上需要的最少數量為 2 ，即 49 + 49");
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}
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