Array_product-of-array-except-self.cpp

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.

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.)


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https://leetcode.com/problems/product-of-array-except-self/
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class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        
    int n = nums.size();
    std::vector<int> answer(n, 0);

    // Calculate the prefix products
    int prefix_product = 1;
    for (int i = 0; i < n; ++i) {
        answer[i] = prefix_product;
        prefix_product *= nums[i];
    }

    // Calculate the suffix products and multiply them with the prefix products
    int suffix_product = 1;
    for (int i = n - 1; i >= 0; --i) {
        answer[i] *= suffix_product;
        suffix_product *= nums[i];
    }

    return answer;

    }
};