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49 lines
1.5 KiB
Python
49 lines
1.5 KiB
Python
"""
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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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"""零钱兑换：贪心"""
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# 假设 coins 列表有序
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i = len(coins) - 1
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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 and coins[i] > amt:
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i -= 1
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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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# 若未找到可行方案，则返回 -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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# 贪心：能够保证找到全局最优解
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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"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 = coin_change_greedy(coins, amt)
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print(f"\ncoins = {coins}, amt = {amt}")
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print(f"凑到 {amt} 所需的最少硬币数量为 {res}")
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print(f"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 = coin_change_greedy(coins, amt)
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print(f"\ncoins = {coins}, amt = {amt}")
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print(f"凑到 {amt} 所需的最少硬币数量为 {res}")
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print(f"实际上需要的最少数量为 2 ，即 49 + 49")
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