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55 lines
1.7 KiB
Swift
55 lines
1.7 KiB
Swift
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/**
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* File: coin_change_greedy.swift
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* Created Time: 2023-09-03
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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/* 零钱兑换：贪心 */
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func coinChangeGreedy(coins: [Int], amt: Int) -> Int {
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// 假设 coins 列表有序
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var i = coins.count - 1
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var count = 0
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var amt = amt
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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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return amt == 0 ? count : -1
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}
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@main
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enum CoinChangeGreedy {
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/* Driver Code */
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static func main() {
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// 贪心：能够保证找到全局最优解
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var coins = [1, 5, 10, 20, 50, 100]
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var amt = 186
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var res = coinChangeGreedy(coins: coins, amt: amt)
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print("\ncoins = \(coins), amount = \(amt)")
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print("凑到 \(amt) 所需的最少硬币数量为 \(res)")
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// 贪心：无法保证找到全局最优解
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coins = [1, 20, 50]
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amt = 60
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res = coinChangeGreedy(coins: coins, amt: amt)
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print("\ncoins = \(coins), amount = \(amt)")
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print("凑到 \(amt) 所需的最少硬币数量为 \(res)")
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print("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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coins = [1, 49, 50]
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amt = 98
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res = coinChangeGreedy(coins: coins, amt: amt)
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print("\ncoins = \(coins), amount = \(amt)")
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print("凑到 \(amt) 所需的最少硬币数量为 \(res)")
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print("实际上需要的最少数量为 2 ，即 49 + 49")
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}
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}
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