Product of Array Exclude Itself

Given an integers array A.

Define B[i] = A[0] * … * A[i-1] * A[i+1] * … * A[n-1], calculate B WITHOUT divide operation.

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Example
For A = [1, 2, 3], return [6, 3, 2].

public class Solution {    /**     * @param A: Given an integers array A     * @return: A Long array B and B[i]= A[0] * ... * A[i-1] * A[i+1] * ... * A[n-1]     */    public ArrayList<Long> productExcludeItself(ArrayList<Integer> A) {        // write your code        ArrayList<Long> res = new ArrayList<Long>();        if (A==null || A.size()==0 ) return res;        long[] lProduct = new long[A.size()];        long[] rProduct = new long[A.size()];        lProduct[0] = 1;        for (int i=1; i<A.size(); i++) {            lProduct[i] = lProduct[i-1]*A.get(i-1);//left 累×        }        rProduct[A.size()-1] = 1;//right 累×        for (int j=A.size()-2; j>=0; j--) {            rProduct[j] = rProduct[j+1]*A.get(j+1);        }        for (int k=0; k<A.size(); k++) {            res.add(lProduct[k] * rProduct[k]);        }        return res;    }}