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238. Product of Array Except Self
Medium
Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].
The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
You must write an algorithm that runs in O(n) time and without using the division operation.
Example 1:
Input: nums = [1,2,3,4]
Output: [24,12,8,6]
Example 2:
Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]
Constraints:
2 <= nums.length <= 105-30 <= nums[i] <= 30- The product of any prefix or suffix of
numsis guaranteed to fit in a 32-bit integer.
Follow up: Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)
Solution
public class Solution {
public int[] ProductExceptSelf(int[] nums) {
int product = 1;
int[] ans = new int[nums.Length];
foreach (int num in nums) {
product = product * num;
}
for (int i = 0; i < nums.Length; i++) {
if (nums[i] != 0) {
ans[i] = product / nums[i];
} else {
int p = 1;
for (int j = 0; j < nums.Length; j++) {
if (j != i) {
p = p * nums[j];
}
}
ans[i] = p;
}
}
return ans;
}
}