Product of Array Except Self

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]

Solution

class Solution {

public int[] productExceptSelf(int[] nums) {

int n = nums.length;

int[] ans = new int[n];

Arrays.fill(ans, 1);

// left side product

int curr = 1;

for(int i=0; i<n; i++) {

ans[i] = ans[i] * curr;

curr = curr * nums[i];

}

// right side product

curr = 1;

for(int i=n-1; i>=0; i--) {

ans[i] = ans[i] * curr;

curr = curr * nums[i];

}

return ans;

}

}