238. Product of Array Except Self

Solved

Medium

Topics

Companies

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.)

ping

Solution

class Solution {

    /**
    Time : O(n)
    Space : O(1)
     */
    public int[] productExceptSelf(int[] nums) {

        int n=nums.length,indexAtZeroIsPresent=-1,prod=1,Zcount=0;
        for(int i=0;i<n;i++){
            if(nums[i]==0) {indexAtZeroIsPresent=i; Zcount++;}
            else prod*=nums[i];
        }

        for(int i=0;i<n;i++){
            if(nums[i]!=0)
              nums[i]=Zcount>0 ? 0 : prod/nums[i];
        }
        if(Zcount==1) nums[indexAtZeroIsPresent]=prod;
        
        return nums;

    }
}

/**
238. Product of Array Except Self
Solved
Medium
Topics
Companies
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.)


 */