构建乘积数组

题目描述
给定一个数组A[0,1,...,n-1],请构建一个数组B[0,1,...,n-1],其中B中的元素B[i]=A[0]A[1]...A[i-1]A[i+1]...A[n-1]。不能使用除法。

public class Solution {
    
    public int[] multiply(int[] A) {
        
        if(A == null || A.length == 0){
            
            return A;
        }
        int[] left = new int[A.length];
        int[] right = new int[A.length];
        int num = 1;
        for(int i = 0; i < A.length; i++) {
            
            left[i] = num;
            num *= A[i];
        }
        num = 1;
        for(int i = A.length - 1; i >=0; i--){
            
            right[i] = num;
            num *= A[i];
        }
        int[] B = new int[A.length];
        for(int i = 0; i < A.length; i++) {
            
            B[i] = left[i] * right[i];
        }
        return B;
    }
}