Wet Shark and Two Subsequences

ai+bi = R
ai-bi = S
2ai = R+S
2bi = R-S

然后就是DP，如果用二维数组的话，注意计算的方向，防止覆盖dp数组的值

def twoSubsequences(x, r, s):if r<s or (r+s)%2: return 0mod=10**9+7sa,sb=(r+s)//2,(r-s)//2maxL=sb//min(x)maxV=sadp=[[0 for _ in range(maxV+1)] for _ in range(maxL+1)]dp[0][0]=1for j in x:for l in range(maxL,0,-1): # 1, maxL+1for i in range(maxV,-1,-1):if i>=j: dp[l][i]+=dp[l-1][i-j]dp[l][i]%=modres=0for l in range(1, maxL+1):res+=dp[l][sa]*dp[l][sb]res%=modreturn resif __name__ == '__main__':mrs = input().split()m = int(mrs[0])r = int(mrs[1])s = int(mrs[2])x = list(map(int, input().rstrip().split()))result = twoSubsequences(x, r, s)print(result)#print(twoSubsequences([1,1,1,2], 3, 1))
#print(twoSubsequences([1,1,1,4], 3, 5))
#print(twoSubsequences([1,1,1,4], 5, 3))

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