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53 lines
1.6 KiB
53 lines
1.6 KiB
8 months ago
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/**
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* File: coin_change_greedy.kt
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* Created Time: 2024-01-25
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* Author: curtishd (1023632660@qq.com)
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*/
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package chapter_greedy
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/* 零錢兌換：貪婪 */
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fun coinChangeGreedy(coins: IntArray, amt: Int): Int {
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// 假設 coins 串列有序
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var am = amt
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var i = coins.size - 1
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var 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 (am > 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] > am) {
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i--
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}
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// 選擇 coins[i]
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am -= coins[i]
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count++
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}
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// 若未找到可行方案，則返回 -1
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return if (am == 0) count else -1
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}
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/* Driver Code */
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fun main() {
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// 貪婪：能夠保證找到全域性最優解
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var coins = intArrayOf(1, 5, 10, 20, 50, 100)
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var amt = 186
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var res = coinChangeGreedy(coins, amt)
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println("\ncoins = ${coins.contentToString()}, amt = $amt")
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println("湊到 $amt 所需的最少硬幣數量為 $res")
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// 貪婪：無法保證找到全域性最優解
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coins = intArrayOf(1, 20, 50)
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amt = 60
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res = coinChangeGreedy(coins, amt)
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println("\ncoins = ${coins.contentToString()}, amt = $amt")
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println("湊到 $amt 所需的最少硬幣數量為 $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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coins = intArrayOf(1, 49, 50)
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amt = 98
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res = coinChangeGreedy(coins, amt)
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println("\ncoins = ${coins.contentToString()}, amt = $amt")
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println("湊到 $amt 所需的最少硬幣數量為 $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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