Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
Example:
Input:[1,2,3,4]Output:[24,12,8,6]
Note: Please solve it without division and in O(n).
Follow up:
Could you solve it with constant space complexity? (The output array does notcount as extra space for the purpose of space complexity analysis.)
Solution:
Building left side product list & right side product list.
Times two lists together.
class Solution { public int[] productExceptSelf(int[] nums) { int n = nums.length; int[] leftSide = new int[n]; leftSide[0] = 1; for (int i = 1; i < n; i++) { leftSide[i] = leftSide[i - 1] * nums[i - 1]; } int[] rightSide = new int[n]; rightSide[n - 1] = 1; for (int i = n - 2; i >= 0; i--) { rightSide[i] = rightSide[i + 1] * nums[i + 1]; } int[] res = new int[n]; for (int i = 0; i < n; i++) { res[i] = leftSide[i] * rightSide[i]; } return res; } }
Time complexity: O(n).
Space complexity: O(n).
Android Playground 