LeetCode-in-All
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
class Solution {
/**
* @param Integer[] $nums
* @return Integer[]
*/
public function productExceptSelf($nums) {
$product = 1;
$ans = array_fill(0, count($nums), 0);
foreach ($nums as $num) {
$product = $product * $num;
}
for ($i = 0; $i < count($nums); $i++) {
if ($nums[$i] != 0) {
$ans[$i] = $product / $nums[$i];
} else {
$p = 1;
for ($j = 0; $j < count($nums); $j++) {
if ($j != $i) {
$p = $p * $nums[$j];
}
}
$ans[$i] = $p;
}
}
return $ans;
}
}