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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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/* 零钱兑换：贪心 */
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fn coin_change_greedy(coins: &[i32], mut amt: i32) -> i32 {
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// 假设 coins 列表有序
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let mut i = coins.len() - 1;
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let mut count = 0;
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// 循环进行贪心选择，直到无剩余金额
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while amt > 0 {
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// 找到小于且最接近剩余金额的硬币
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while i > 0 && coins[i] > amt {
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i -= 1;
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}
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// 选择 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，则返回 -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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// 贪心：能够保证找到全局最优解
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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!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
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// 贪心：无法保证找到全局最优解
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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!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
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println!("实际上需要的最少数量为 3 ，即 20 + 20 + 20");
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// 贪心：无法保证找到全局最优解
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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!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
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println!("实际上需要的最少数量为 2 ，即 49 + 49");
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}
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