题解 | #目标和#

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param nums int整型一维数组 
# @param target int整型 
# @return int整型
#
class Solution:
    def findTargetSumWays(self , nums: List[int], target: int) -> int:
        # write code here
        total = sum(nums)
        return 0 if total <target or (total&1)^(target&1)!=0 or len(nums)==0 else self.subset(nums,(total+target)>>1)

    def subset(self,nums,target):
        if target<0:
            return 0
        dp = [0] * (target+1)
        dp[0] = 1
        for n in nums:
            for j in range(target,n-1,-1):
                dp[j] += dp[j-n]
        return dp[target]