LeetCode: 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]

 

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.

Solution:

class Solution {

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

int[] pr = new int[nums.length];

int[] sf = new int[nums.length];

int[] res = new int[nums.length];

int prc = 0;

int sfc = nums.length - 1;

while(prc < nums.length){

if(prc == 0){

pr[prc] = 1;

}else{

pr[prc] = pr[prc - 1] * nums[prc - 1];

}

if(sfc == nums.length - 1){

sf[sfc] = 1;

}else{

sf[sfc] = sf[sfc + 1] * nums[sfc + 1];

}

prc++;

sfc--;

}

for(int i= nums.length - 1; i >= 0; i--){

System.out.println(sf[i]+" "+pr[i]);

res[i] = pr[i] * sf[i];

}

return res;

}

}