代码随想训练营第四十三天（Python）｜ 1049.最后一块石头的重量II、 494. 目标和 、 474.一和零

1049.最后一块石头的重量II

class Solution:
    def lastStoneWeightII(self, stones: List[int]) -> int:
        total = sum(stones)
        target = total // 2
        dp = [0] * (target + 1)

        for stone in stones:
            for j in range(target, stone - 1, -1):
                dp[j] = max(dp[j], dp[j-stone] + stone)
        return total - dp[target] - dp[target]

494. 目标和

class Solution:
    def findTargetSumWays(self, nums: List[int], target: int) -> int:
        total = sum(nums)
        # 排除边界情况
        if abs(target) > total:
            return 0
        if (total + target) % 2 != 0:
            return 0
        # 背包
        left_num = (total + target) // 2
        # dp[j] 代表正数集合为 j 的方法总数为 dp[j]
        # 初始化 dp
        dp = [0] * (left_num + 1)
        dp[0] = 1
        for num in nums:
            for j in range(left_num, num - 1, -1):
                dp[j] += dp[j-num]
        return dp[-1]

474.一和零

class Solution:
    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
        dp = [[0] * (n + 1) for _ in range(m + 1)]
        for s in strs:
            zero_num = s.count("0")
            one_num = s.count("1")
            for i in range(m, zero_num - 1, -1):
                for j in range(n, one_num - 1, -1):
                    dp[i][j] = max(dp[i][j], dp[i - zero_num][j - one_num] + 1)
        return dp[m][n]