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49 lines
1.5 KiB
Python
49 lines
1.5 KiB
Python
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"""
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File: coin_change_greedy.py
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Created Time: 2023-07-18
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Author: krahets (krahets@163.com)
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"""
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def coin_change_greedy(coins: list[int], amt: int) -> int:
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"""零錢兌換：貪婪"""
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# 假設 coins 串列有序
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i = len(coins) - 1
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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 and coins[i] > amt:
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i -= 1
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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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# 若未找到可行方案，則返回 -1
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return count if amt == 0 else -1
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"""Driver Code"""
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if __name__ == "__main__":
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# 貪婪：能夠保證找到全域性最優解
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coins = [1, 5, 10, 20, 50, 100]
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amt = 186
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res = coin_change_greedy(coins, amt)
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print(f"\ncoins = {coins}, amt = {amt}")
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print(f"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 = [1, 20, 50]
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amt = 60
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res = coin_change_greedy(coins, amt)
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print(f"\ncoins = {coins}, amt = {amt}")
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print(f"湊到 {amt} 所需的最少硬幣數量為 {res}")
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print(f"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 = [1, 49, 50]
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amt = 98
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res = coin_change_greedy(coins, amt)
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print(f"\ncoins = {coins}, amt = {amt}")
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print(f"湊到 {amt} 所需的最少硬幣數量為 {res}")
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print(f"實際上需要的最少數量為 2 ，即 49 + 49")
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