leetcode/coins_change.py at main · atib92/leetcode · GitHub

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"""
Coin Change
Solved
Medium
Topics
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You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money.

Return the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1.

You may assume that you have an infinite number of each kind of coin.


Example 1:

Input: coins = [1,2,5], amount = 11
Output: 3
Explanation: 11 = 5 + 5 + 1
Example 2:

Input: coins = [2], amount = 3
Output: -1
Example 3:

Input: coins = [1], amount = 0
Output: 0


Constraints:

1 <= coins.length <= 12
1 <= coins[i] <= 231 - 1
0 <= amount <= 104
"""
class Solution:
    """
    This is a slight modification of "find ways to build amount using coins. Rather than adding, we need to maitain a minimum"
    Time: O(amount*len(coins))
    """
    def coinChange(self, coins: List[int], amount: int) -> int:
        ways = [float("inf")] * (amount+1)
        ways[0] = 0
        for coin in coins:
            for amt in range(1, amount+1):
                if amt >= coin:
                    ways[amt] = min(ways[amt], 1+ways[amt-coin])
        return -1 if ways[amount] == float("inf") else ways[amount]