代码随想录day44|完全背包518. 零钱兑换 II377. 组合总和 Ⅳ

完全背包比0-1背包就改变了遍历顺序，先物品再背包的顺序不再重要，另外遍历背包时不需要从后往前遍历

def test_CompletePack():
    weight = [1, 3, 4]
    value = [15, 20, 30]
    bagWeight = 4
    dp = [0] * (bagWeight + 1)
    for i in range(len(weight)):  # 遍历物品
        for j in range(weight[i], bagWeight + 1):  # 遍历背包容量
            dp[j] = max(dp[j], dp[j - weight[i]] + value[i])
    print(dp[bagWeight])

test_CompletePack()

518. 零钱兑换 II

class Solution:
    def change(self, amount: int, coins: List[int]) -> int:
        dp = [0] * (amount +1)
        dp[0] =1
        for i in coins:
            for j in range(i,amount+1):
                dp[j] += dp[j-i]
        return dp[amount]

377. 组合总和 Ⅳ

class Solution:
    def combinationSum4(self, nums: List[int], target: int) -> int:
        dp = [0] * (target +1)
        dp[0] =1
        for j in range(target+1):
            for i in nums:
                if j>=i:
                    dp[j] += dp[j-i]
        return dp[target]