/
Solution.java
48 lines (45 loc) · 1.47 KB
/
Solution.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
/**
* Time : O(N) ; Space: O(1)
* @tag : Array
* @by : Steven Cooks
* @date: Aug 19, 2015
***************************************************************************
* Description:
*
* Given an array of n integers where n > 1, nums, return an array output
* such that output[i] is equal to the product of all the elements of nums
* except nums[i].
*
* Solve it without division and in O(n).
*
* For example, given [1,2,3,4], return [24,12,8,6].
*
* Follow up:
* Could you solve it with constant space complexity? (Note: The output array
* does not count as extra space for the purpose of space complexity analysis.)
*
***************************************************************************
* {@link https://leetcode.com/problems/product-of-array-except-self/ }
*/
package _238_ProductOfArrayExceptSelf;
/** see test {@link _238_ProductOfArrayExceptSelf.SolutionTest } */
public class Solution {
// res[i] = A[i - 1] * B[i + 1]
// where A[i - 1] = nums[0] * nums[1] * .. * nums[i - 1]
// B[i + 1] = nums[i + 1] * nums[i + 2] * .. nums[len - 1]
public int[] productExceptSelf(int[] nums) {
int n = nums.length;
int[] res = new int[n];
int left = 1;
for (int i = 0; i < n; i++) {
res[i] = left;
left *= nums[i];
}
int right = 1;
for (int i = n - 1; i >= 0; i--) {
res[i] *= right;
right *= nums[i];
}
return res;
}
}