ProductOfArrayExceptSelfSolution

import java.util.*;

class ProductOfArrayExceptSelf{
    public static int[] productOfArrayExceptSelf(int[] nums){
        int n = nums.length;

        if(n<2){
            return new int[] {0};
        }

        int[] left = new int[n];
        int[] right = new int[n];
        int[] res = new int[n];

        left[0] = 1;
        right[n-1] = 1;

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

        for(int i=n-2; i>-1; i--){
            right[i] = right[i+1]*nums[i+1];
        }

        for(int i=0; i<n; i++){
            res[i] = left[i]*right[i];
        }

        return res;

    }

    public static int[] productOfArrayExceptSelfConstantSpace(int[] nums){
        int n = nums.length;

        if(n<2){
            return new int[] {0};
        }

        int[] res = new int[n];

        res[0] = 1;

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

        int right = 1;

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

        return res;

    }

    public static void main(String args[]){
        int[] nums = {1,2,3,4};
        System.out.println(Arrays.toString(productOfArrayExceptSelf(nums)));
        System.out.println(Arrays.toString(productOfArrayExceptSelfConstantSpace(nums)));
    }
}