problem_238.java

/*
238. Product of Array Except SelfGiven 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.
 */

class Solution {
    public int[] productExceptSelf(int[] nums) {
        int n = nums.length;
        int[] result = new int[n];
        result[0] = 1;
        for (int i = 1; i < n; i++) {
            result[i] = result[i - 1] * nums[i - 1];
        }
        int right = 1;
        for (int i = n - 1; i >= 0; i--) {
            result[i] = result[i] * right;
            right *= nums[i];
        }
        return result;
    }
}