【朱迪的LeetCode刷题笔记】238. Product of Array Except Self #Medium #Python #C++

Judie

Given an integer array nums, return an array answer such that answer<i> is equal to the product of all the elements of nums except nums<i>.

The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

You must write an algorithm that runs in O(n) time and without using the division operation.

[i][i]Example 1:
Input: nums = [1,2,3,4]
Output: [24,12,8,6]

Example 2:
Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]

Constraints:
2 <= nums.length <= 105
-30 <= nums<i> <= 30
The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

Follow up:
Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)

Judy
Python

class Solution(object):
    def productExceptSelf(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        a = 1
        b = 1
        l = len(nums)
        answer = []
        for x in nums:
            answer.append(a)
            a *= x
        for i in range(l-1, -1, -1):
            answer[i] *= b
            b *= nums[i]
        return answer

Mike
C++

vector<int> productExceptSelf(vector<int>& nums) {
        vector<int> result;
        int prod = 1;
        for (auto i : nums) {
            result.push_back(prod);
            prod = i;
        }
        prod = 1;
        for (int i = nums.size() - 1; i >= 0; i--) {
            result[i]= prod;
            prod *= nums[i];
        }
        return result;
    }