ProductOfArrayExceptSelf.java

public class ProductOfArrayExceptSelf {

    // Time Complexity: O(n)
    // Space Complexity: O(1)
    public int[] productExceptSelf(int[] nums) {
        int n = nums.length;
        int[] res = new int[n];

        res[0] = 1;
        for (int i = 1; i < n; i++) {
            res[i] = res[i - 1] * nums[i - 1];
        }

        int postfix = 1;
        for (int i = n - 1; i >= 0; i--) {
            res[i] *= postfix;
            postfix *= nums[i];
        }
        return res;
    }

    /*
    Brute Force Approach

    // Time Complexity: O(n^2)
    // Space Complexity: O(1)

    public int[] productExceptSelf(int[] nums) {
        int n = nums.length;
        int[] res = new int[n];

        for (int i = 0; i < n; i++) {
            int prod = 1;
            for (int j = 0; j < n; j++) {
                if (i != j) {
                    prod *= nums[j];
                }
            }
            res[i] = prod;
        }
        return res;
    }
     */

    public static void main(String[] args) {

    }
}