hello-algo/codes/rust/chapter_greedy/coin_change_greedy.rs
2023-07-26 10:01:49 +08:00

54 lines
1.6 KiB
Rust

/*
* File: coin_change_greedy.rs
* Created Time: 2023-07-22
* Author: night-cruise (2586447362@qq.com)
*/
/* 零钱兑换:贪心 */
fn coin_change_greedy(coins: &[i32], mut amt: i32) -> i32 {
// 假设 coins 列表有序
let mut i = coins.len() - 1;
let mut count = 0;
// 循环进行贪心选择,直到无剩余金额
while amt > 0 {
// 找到小于且最接近剩余金额的硬币
while coins[i] > amt {
i -= 1;
}
// 选择 coins[i]
amt -= coins[i];
count += 1;
}
// 若未找到可行方案,则返回 -1
if amt == 0 {
count
} else {
-1
}
}
/* Driver Code */
fn main() {
// 贪心:能够保证找到全局最优解
let coins = [1, 5, 10, 20, 50, 100];
let amt = 186;
let res = coin_change_greedy(&coins, amt);
println!("\ncoins = {:?}, amt = {}", coins, amt);
println!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
// 贪心:无法保证找到全局最优解
let coins = [1, 20, 50];
let amt = 60;
let res = coin_change_greedy(&coins, amt);
println!("\ncoins = {:?}, amt = {}", coins, amt);
println!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
println!("实际上需要的最少数量为 3 ,即 20 + 20 + 20");
// 贪心:无法保证找到全局最优解
let coins = [1, 49, 50];
let amt = 98;
let res = coin_change_greedy(&coins, amt);
println!("\ncoins = {:?}, amt = {}", coins, amt);
println!("凑到 {} 所需的最少硬币数量为 {}", amt, res);
println!("实际上需要的最少数量为 2 ,即 49 + 49");
}