238. 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] 

class Solution {

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

int n = nums.length;

int[] prefix = new int[n];

int[] sufix = new int[n];

int[] res = new int[n];

prefix[0] = 1;

for(int i = 1;i<n;i++){

prefix[i] = prefix[i-1] * nums[i-1];

}

sufix[n - 1] = 1;

for(int i = n - 2;i>= 0;i--){

sufix[i] = sufix[i+1] * nums[i+1];

}

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

res[i] = prefix[i] * sufix[i];

}

return res;

}

}