[Python知识库]剑指Offer：构建乘积数组

Python Reduce (out of time)

class Solution(object):
    def constructArr(self, a):
        """
        :type a: List[int]
        :rtype: List[int]
        """
        B = []
        if len(a) == 0:
            return B
        else:
            for i in range(len(a)):
                tmp = a[i]
                a[i] = 1
                B.append(reduce(lambda x,y:x*y, a))
                a[i] = tmp
        return B

分为上下三角：（不可以x, y, b 连续赋值，因为指针指向同一存储空间）?

class Solution(object):
    def constructArr(self, a):
        """
        :type a: List[int]
        :rtype: List[int]
        """
        n = len(a)
        x = [1] * n
        y = [1] * n
        b = [1] * n
        for i in range(1, n):
            x[i] = x[i-1] * a[i-1]
        for j in range(n-2, -1, -1):
            y[j] = y[j+1] * a[j+1]
        for i in range(n):
            b[i] = x[i] * y[i]

        return b