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.

Example

For A = [1, 2, 3], return [6, 3, 2].

分析：

 public class Solution {
     public int[] productExceptSelf(int[] A) {
         int[] left = new int[A.length];
         int[] right = new int[A.length];
         int[] result = new int[A.length];

         for (int i = ; i < A.length; i++) {
             left[i] = i ==  ?  : left[i - ] * A[i - ];
             right[A.length -  - i] = (i == ) ?  : right[A.length - i] * A[A.length - i];
         }

         for (int i = ; i < A.length; i++) {
             result[i] = left[i] * right[i];
         }
         return result;
     }
 }

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

one pass

 class Solution {
     public int[] productExceptSelf(int[] nums) {
         int[] result = new int[nums.length];
         Arrays.fill(result, );
         int left = , right = ;
         for (int i = , j = nums.length - ; i < nums.length - ; i++, j--) {
             left *= nums[i];
             right *= nums[j];
             result[i + ] *= left;
             result[j - ] *= right;
         }
         return result;
     }
 }